EN(STI)(diag)-96
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
19.Diagnostic Procedure with Diagnostic Trouble Code (DTC)
A: DTC P000A A CAMSHAFT POSITION SLOW RESPONSE (BANK 1)
NOTE:
For the diagnostic procedure, refer to DTC P0011. <Ref. to EN(STI)(diag)-97, DTC P0011 INTAKE CAM-
SHAFT POSITION - TIMING OVER-ADVANCED OR SYSTEM PERFORMANCE (BANK 1), Diagnostic Pro-
cedure with Diagnostic Trouble Code (DTC).>
B: DTC P000B B CAMSHAFT POSITION SLOW RESPONSE (BANK 1)
NOTE:
For the diagnostic procedure, refer to DTC P0014. <Ref. to EN(STI)(diag)-98, DTC P0014 EXHAUST AVCS
SYSTEM 1 (RANGE/PERFORMANCE), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
C: DTC P000C A CAMSHAFT POSITION SLOW RESPONSE (BANK 2)
NOTE:
For the diagnostic procedure, refer to DTC P0021. <Ref. to EN(STI)(diag)-103, DTC P0021 INTAKE CAM-
SHAFT POSITION - TIMING OVER-ADVANCED OR SYSTEM PERFORMANCE (BANK 2), Diagnostic Pro-
cedure with Diagnostic Trouble Code (DTC).>
D: DTC P000D B CAMSHAFT POSITION SLOW RESPONSE (BANK 2)
NOTE:
For the diagnostic procedure, refer to DTC P0024. <Ref. to EN(STI)(diag)-104, DTC P0024 EXHAUST
AVCS SYSTEM 2 (RANGE/PERFORMANCE), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
15WRX_STI_US_EN.book 96 ペー   
EN(STI)(diag)-97
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
E: DTC P0011 INTAKE CAMSHAFT POSITION - TIMING OVER-ADVANCED OR
SYSTEM PERFORMANCE (BANK 1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-16, DTC P0011 INTAKE CAMSHAFT POSITION - TIMING
OVER-ADVANCED OR SYSTEM PERFORMANCE (BANK 1), Diagnostic Trouble Code (DTC) Detecting
Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine and let it idle.
2) Read the value of «VVT Adv. Ang. Amount
R» using the Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «VVT Adv. Ang.
Amount R» approx. 0 deg?
Go to step 2. Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Intake camshaft
(dirt, damage of
camshaft)
2 CHECK CURRENT DATA.
1) Drive with acceleration and deceleration at
80 km/h (50 MPH) or less.
NOTE:
Drive to an extent that the duty output of oil flow
control solenoid valve increases.
2) Read the values of «OCV Duty R» and
«VVT Adv. Ang. Amount R» using the Subaru
Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
When the value of «OCV Duty
R» increases more than 10%,
is the value of «VVT Adv. Ang.
Amount R» approx. 0 deg?
Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Intake camshaft
(dirt, damage of
camshaft)
Perform the follow-
ing procedures,
and clean the oil
routing.
Replace the
engine oil and idle
the engine for 5
minutes, and then
replace the oil filter
and engine oil.
<Ref. to LU(STI)-
11, REPLACE-
MENT, Engine
Oil.> <Ref. to
LU(STI)-29,
Engine Oil Filter.>
15WRX_STI_US_EN.book 97 ペー   
EN(STI)(diag)-98
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
F: DTC P0014 EXHAUST AVCS SYSTEM 1 (RANGE/PERFORMANCE)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-17, DTC P0014 EXHAUST AVCS SYSTEM 1 (RANGE/
PERFORMANCE), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine and let it idle.
2) Read the value of «Exh. VVT Retard Ang.
R» using the Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Exh. VVT
Retard Ang. R» approx. 0 deg?
Go to step 2. Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Exhaust cam-
shaft (dirt, dam-
age of camshaft)
2 CHECK CURRENT DATA.
1) Drive with acceleration and deceleration at
80 km/h (50 MPH) or less.
NOTE:
Drive to an extent that the duty output of oil flow
control solenoid valve increases.
2) Read the values of «Exh. OCV Duty R» and
«Exh. VVT Retard Ang. R» using the Subaru
Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
When the value of «Exh. OCV
Duty R» increases more than
10%, is the value of «Exh. VVT
Retard Ang. R» approx. 0 deg?
Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Exhaust cam-
shaft (dirt, dam-
age of camshaft)
Perform the follow-
ing procedures,
and clean the oil
routing.
Replace the
engine oil and idle
the engine for 5
minutes, and then
replace the oil filter
and engine oil.
<Ref. to LU(STI)-
11, REPLACE-
MENT, Engine
Oil.> <Ref. to
LU(STI)-29,
Engine Oil Filter.>
15WRX_STI_US_EN.book 98 ペー   
EN(STI)(diag)-99
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
G: DTC P0016 CRANKSHAFT POSITION - CAMSHAFT POSITION CORRELA-
TION (BANK1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-18, DTC P0016 CRANKSHAFT POSITION - CAMSHAFT
POSITION CORRELATION (BANK1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine and let it idle.
2) Read the values of «VVT Adv. Ang. Amount
R» and «OCV Duty R» using the Subaru Select
Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «VVT Adv. Ang.
Amount R» approx. 0 deg, and
the value of «OCV Duty R»
approx. 10%?
Perform the follow-
ing procedures,
and clean the oil
routing.
Replace the
engine oil and idle
the engine for 5
minutes, and then
replace the oil filter
and engine oil.
<Ref. to LU(STI)-
11, REPLACE-
MENT, Engine
Oil.> <Ref. to
LU(STI)-29,
Engine Oil Filter.>
Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Intake camshaft
(dirt, damage of
camshaft)
Timing belt
(matching of timing
mark)
15WRX_STI_US_EN.book 99 ペー   
EN(STI)(diag)-100
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
H: DTC P0017 CRANK AND CAM TIMING B SYSTEM FAILURE (BANK 1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-20, DTC P0017 CRANK AND CAM TIMING B SYSTEM
FAILURE (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine and let it idle.
2) Read the values of «Exh. VVT Retard Ang.
R» and «Exh. OCV Duty R» using the Subaru
Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Exh. VVT
Retard Ang. R» approx. 0 deg,
and the value of «Exh. OCV
Duty R» approx. 10%?
Perform the follow-
ing procedures,
and clean the oil
routing.
Replace the
engine oil and idle
the engine for 5
minutes, and then
replace the oil filter
and engine oil.
<Ref. to LU(STI)-
11, REPLACE-
MENT, Engine
Oil.> <Ref. to
LU(STI)-29,
Engine Oil Filter.>
Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Exhaust cam-
shaft (dirt, dam-
age of camshaft)
Timing belt
(matching of timing
mark)
15WRX_STI_US_EN.book 100 ージ 20  
EN(STI)(diag)-101
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
I: DTC P0018 CRANKSHAFT POSITION - CAMSHAFT POSITION CORRELA-
TION (BANK2)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-21, DTC P0018 CRANKSHAFT POSITION - CAMSHAFT
POSITION CORRELATION (BANK2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine and let it idle.
2) Read the values of «VVT Adv. Ang. Amount
L» and «OCV Duty L» using the Subaru Select
Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «VVT Adv. Ang.
Amount L» approx. 0 deg, and
the value of «OCV Duty L»
approx. 10%?
Perform the follow-
ing procedures,
and clean the oil
routing.
Replace the
engine oil and idle
the engine for 5
minutes, and then
replace the oil filter
and engine oil.
<Ref. to LU(STI)-
11, REPLACE-
MENT, Engine
Oil.> <Ref. to
LU(STI)-29,
Engine Oil Filter.>
Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Intake camshaft
(dirt, damage of
camshaft)
Timing belt
(matching of timing
mark)
15WRX_STI_US_EN.book 101 ージ 20  
EN(STI)(diag)-102
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
J: DTC P0019 CRANK AND CAM TIMING B SYSTEM FAILURE (BANK 2)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-21, DTC P0019 CRANK AND CAM TIMING B SYSTEM
FAILURE (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine and let it idle.
2) Read the values of «Exh. VVT Retard Ang.
L» and «Exh. OCV Duty L» using the Subaru
Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Exh. VVT
Retard Ang. L» approx. 0 deg,
and the value of «Exh. OCV
Duty L» approx. 10%?
Perform the follow-
ing procedures,
and clean the oil
routing.
Replace the
engine oil and idle
the engine for 5
minutes, and then
replace the oil filter
and engine oil.
<Ref. to LU(STI)-
11, REPLACE-
MENT, Engine
Oil.> <Ref. to
LU(STI)-29,
Engine Oil Filter.>
Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Exhaust cam-
shaft (dirt, dam-
age of camshaft)
Timing belt
(matching of timing
mark)
15WRX_STI_US_EN.book 102 ージ 20  
EN(STI)(diag)-103
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
K: DTC P0021 INTAKE CAMSHAFT POSITION - TIMING OVER-ADVANCED OR
SYSTEM PERFORMANCE (BANK 2)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-21, DTC P0021 INTAKE CAMSHAFT POSITION - TIMING
OVER-ADVANCED OR SYSTEM PERFORMANCE (BANK 2), Diagnostic Trouble Code (DTC) Detecting
Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine and let it idle.
2) Read the value of «VVT Adv. Ang. Amount
L» using the Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «VVT Adv. Ang.
Amount L» approx. 0 deg?
Go to step 2. Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Intake camshaft
(dirt, damage of
camshaft)
2 CHECK CURRENT DATA.
1) Drive with acceleration and deceleration at
80 km/h (50 MPH) or less.
NOTE:
Drive to an extent that the duty output of oil flow
control solenoid valve increases.
2) Read the values of «OCV Duty L» and «VVT
Adv. Ang. Amount L» using the Subaru Select
Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
When the value of «OCV Duty
L» increases more than 10%, is
the value of «VVT Adv. Ang.
Amount L» approx. 0 deg?
Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Intake camshaft
(dirt, damage of
camshaft)
Perform the follow-
ing procedures,
and clean the oil
routing.
Replace the
engine oil and idle
the engine for 5
minutes, and then
replace the oil filter
and engine oil.
<Ref. to LU(STI)-
11, REPLACE-
MENT, Engine
Oil.> <Ref. to
LU(STI)-29,
Engine Oil Filter.>
15WRX_STI_US_EN.book 103 ージ 20  
EN(STI)(diag)-104
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
L: DTC P0024 EXHAUST AVCS SYSTEM 2 (RANGE/PERFORMANCE)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-21, DTC P0024 EXHAUST AVCS SYSTEM 2 (RANGE/
PERFORMANCE), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine and let it idle.
2) Read the value of «Exh. VVT Retard Ang.
L» using the Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Exh. VVT
Retard Ang. L» approx. 0 deg?
Go to step 2. Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Exhaust cam-
shaft (dirt, dam-
age of camshaft)
2 CHECK CURRENT DATA.
1) Drive with acceleration and deceleration at
80 km/h (50 MPH) or less.
NOTE:
Drive to an extent that the duty output of oil flow
control solenoid valve increases.
2) Read the values of «Exh. OCV Duty L» and
«Exh. VVT Retard Ang. L» using the Subaru
Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
When the value of «Exh. OCV
Duty L» increases more than
10%, is the value of «Exh. VVT
Retard Ang. L» approx. 0 deg?
Check the follow-
ing item and repair
or replace if neces-
sary.
Oil pipe (clog)
Oil flow control
solenoid valve
(clog or dirt of oil
routing, setting of
spring)
Exhaust cam-
shaft (dirt, dam-
age of camshaft)
Perform the follow-
ing procedures,
and clean the oil
routing.
Replace the
engine oil and idle
the engine for 5
minutes, and then
replace the oil filter
and engine oil.
<Ref. to LU(STI)-
11, REPLACE-
MENT, Engine
Oil.> <Ref. to
LU(STI)-29,
Engine Oil Filter.>
15WRX_STI_US_EN.book 104 ージ 20  
EN(STI)(diag)-105
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
M: DTC P0030 HO2S HEATER CONTROL CIRCUIT (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-22, DTC P0030 HO2S HEATER CONTROL CIRCUIT
(BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 105 ージ 20  
EN(STI)(diag)-106
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Start and warm up the engine.
2) Turn the ignition switch to OFF.
3) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
4) Measure the resistance of harness between
ECM connector and front oxygen (A/F) sensor
connector.
Connector & terminal
(B136) No. 5 — (B379) No. 2:
(B136) No. 6 — (B379) No. 2:
(B136) No. 18 — (B379) No. 3:
(B136) No. 19 — (B379) No. 4:
Is the resistance less than 1 Ω? Go to step 2. Repair the open
circuit of harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
2 CHECK FRONT OXYGEN (A/F) SENSOR.
Measure the resistance between front oxygen
(A/F) sensor terminals.
Terminals
No. 1 — No. 2:
Is the resistance less than 2 —
3 Ω?
Go to step 3. Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
3 CHECK FOR POOR CONTACT.
Check for poor contact of ECM and front oxygen
(A/F) sensor connector.
Is there poor contact of ECM or
front oxygen (A/F) sensor con-
nector?
Repair the poor
contact of ECM or
front oxygen (A/F)
sensor connector.
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
15WRX_STI_US_EN.book 106 ージ 20  
EN(STI)(diag)-107
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
N: DTC P0031 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-23, DTC P0031 HO2S HEATER CONTROL CIRCUIT LOW
(BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 107 ージ 20  
EN(STI)(diag)-108
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK POWER SUPPLY TO FRONT OXY-
GEN (A/F) SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from front oxy-
gen (A/F) sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between front oxygen
(A/F) sensor connector and engine ground.
Connector & terminal
(B379) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 2. Repair the power
supply line.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
A/F, oxygen sen-
sor relay and front
oxygen (A/F) sen-
sor connector
Poor contact of
A/F, oxygen sen-
sor relay connector
Malfunction of A/
F, oxygen sensor
relay
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and front oxygen (A/F) sensor connector.
Connector & terminal
(B136) No. 5 — (B379) No. 2:
(B136) No. 6 — (B379) No. 2:
Is the resistance less than 1 Ω? Go to step 3. Repair the open
circuit of harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
3 CHECK GROUND CIRCUIT FOR ECM.
Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B134) No. 3 — Chassis ground:
(B134) No. 4 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 3 — Chassis ground:
Is the resistance less than 5 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
coupling connector
4 CHECK FRONT OXYGEN (A/F) SENSOR.
Measure the resistance between front oxygen
(A/F) sensor terminals.
Terminals
No. 1 — No. 2:
Is the resistance 2 — 3 Ω? Repair the poor
contact of ECM
connector.
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
15WRX_STI_US_EN.book 108 ージ 20  
EN(STI)(diag)-109
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
O: DTC P0032 HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-24, DTC P0032 HO2S HEATER CONTROL CIRCUIT HIGH
(BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 109 ージ 20  
EN(STI)(diag)-110
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 5 (+) — Chassis ground (–):
(B136) No. 6 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
Go to step 2.
2 CHECK GROUND CIRCUIT FOR ECM.
1) Disconnect the connector from ECM.
2) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 3 — Chassis ground:
(B134) No. 4 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 3 — Chassis ground:
Is the resistance less than 5 Ω? Repair the poor
contact of ECM
connector.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
coupling connector
15WRX_STI_US_EN.book 110 ージ 20  
EN(STI)(diag)-111
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
P: DTC P0037 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-25, DTC P0037 HO2S HEATER CONTROL CIRCUIT LOW
(BANK 1 SENSOR 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 111 ージ 20  
EN(STI)(diag)-112
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK POWER SUPPLY TO REAR OXY-
GEN SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from rear oxygen
sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between rear oxygen
sensor connector and engine ground.
Connector & terminal
(T6) No. 2 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 2. Repair the power
supply line.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
A/F, oxygen sen-
sor relay and rear
oxygen sensor
connector
Poor contact of
A/F, oxygen sen-
sor relay connector
Poor contact of
coupling connector
Malfunction of A/
F, oxygen sensor
relay
2 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and rear oxygen sensor connector.
Connector & terminal
(B135) No. 6 — (T6) No. 1:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
coupling connector
3 CHECK GROUND CIRCUIT FOR ECM.
Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B134) No. 3 — Chassis ground:
(B134) No. 4 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 3 — Chassis ground:
Is the resistance less than 5 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
ECM connector
Poor contact of
coupling connector
4 CHECK REAR OXYGEN SENSOR.
Measure the resistance between rear oxygen
sensor terminals.
Terminals
No. 1 — No. 2:
Is the resistance 5 — 6.4 Ω? Repair the poor
contact of ECM
connector.
Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
15WRX_STI_US_EN.book 112 ージ 20  
EN(STI)(diag)-113
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Q: DTC P0038 HO2S HEATER CONTROL CIRCUIT HIGH (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-26, DTC P0038 HO2S HEATER CONTROL CIRCUIT HIGH
(BANK 1 SENSOR 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 113 ージ 20  
EN(STI)(diag)-114
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B135) No. 6 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and rear
oxygen sensor
connector.
Go to step 2.
2 CHECK GROUND CIRCUIT FOR ECM.
1) Disconnect the connector from ECM.
2) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 3 — Chassis ground:
(B134) No. 4 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 3 — Chassis ground:
Is the resistance less than 5 Ω? Repair the poor
contact of ECM
connector.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
coupling connector
15WRX_STI_US_EN.book 114 ージ 20  
EN(STI)(diag)-115
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
R: DTC P0068 MAP/MAF - THROTTLE POSITION CORRELATION
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-27, DTC P0068 MAP/MAF - THROTTLE POSITION COR-
RELATION, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK AIR INTAKE SYSTEM. Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
Go to step 2.
2 CHECK MANIFOLD ABSOLUTE PRESSURE
SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Read the value of «Mani. Absolute Pres-
sure» using the Subaru Select Monitor or a gen-
eral scan tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
“General Scan Tool Instruction Manual”.
Is the value in «Mani. Absolute
Pressure» 73.3 — 106.6 kPa
(550 — 800 mmHg, 21.65 —
31.50 inHg) when the ignition is
turned ON, and 20.0 — 46.7
kPa (150 — 350 mmHg, 5.91 —
13.78 inHg) during idling?
Go to step 3. Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(STI)-41,
Manifold Absolute
Pressure Sensor.>
3 CHECK THROTTLE OPENING ANGLE.
Using the Subaru Select Monitor or a general
scan tool, read the value in «Throttle Opening
Angle».
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
“General Scan Tool Instruction Manual”.
Is the value in «Throttle Open-
ing Angle» with the throttle fully
closed less than 5%?
Go to step 4. Replace the elec-
tronic throttle con-
trol. <Ref. to
FU(STI)-15, Throt-
tle Body.>
4 CHECK THROTTLE OPENING ANGLE. Is the value in «Throttle Open-
ing Angle» with the throttle fully
open 85% or more?
Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(STI)-41,
Manifold Absolute
Pressure Sensor.>
Replace the elec-
tronic throttle con-
trol. <Ref. to
FU(STI)-15, Throt-
tle Body.>
15WRX_STI_US_EN.book 115 ージ 20  
EN(STI)(diag)-116
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
S: DTC P0071 AMBIENT TEMPERATURE SENSOR CIRCUIT "A" RANGE/PER-
FORMANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-29, DTC P0071 AMBIENT TEMPERATURE SENSOR CIR-
CUIT "A" RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK CURRENT DATA.
1) Turn the ignition switch to ON.
2) Read the value of «Ambient Air Tempera-
ture» using the Subaru Select Monitor or a gen-
eral scan tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For HVAC System”.
<Ref. to AC(diag)-40, Read Current Data.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
3) Read the change of the value in «Ambient
Air Temperature» while heating and cooling the
ambient sensor using a hair dryer.
CAUTION:
Do not heat the part to the temperature
where you cannot touch it with your bare
hand in order to prevent burning yourself
and protect the part.
Does the value of «Ambient Air
Temperature» change between
heating and cooling?
Repair the poor
contact of ECM
connector.
Replace the ambi-
ent sensor. <Ref.
to AC-72, Ambient
Sensor.>
15WRX_STI_US_EN.book 116 ージ 20  
EN(STI)(diag)-117
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
T: DTC P0072 AMBIENT TEMPERATURE SENSOR CIRCUIT "A" LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-31, DTC P0072 AMBIENT TEMPERATURE SENSOR CIR-
CUIT "A" LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
U: DTC P0073 AMBIENT TEMPERATURE SENSOR CIRCUIT "A" HIGH
NOTE:
For the diagnostic procedure, refer to DTC P0072. <Ref. to EN(STI)(diag)-117, DTC P0072 AMBIENT TEM-
PERATURE SENSOR CIRCUIT "A" LOW, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
Step Check Yes No
1 CHECK DTC.
Check for DTC. <Ref. to EN(STI)(diag)-42,
Read Diagnostic Trouble Code (DTC).>
Is DTC P0072 or P0073 dis-
played?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK COMBINATION METER.
Check the combination meter system. <Ref. to
IDI(diag)-2, Basic Diagnostic Procedure.>
Is the combination meter sys-
tem normal?
Repair the poor
contact of ECM
connector.
Repair the combi-
nation meter sys-
tem. <Ref. to
IDI(diag)-2, Basic
Diagnostic Proce-
dure.>
15WRX_STI_US_EN.book 117 ージ 20  
EN(STI)(diag)-118
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
V: DTC P0101 MASS OR VOLUME AIR FLOW CIRCUIT RANGE/PERFOR-
MANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-33, DTC P0101 MASS OR VOLUME AIR FLOW CIRCUIT
RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Engine stalls.
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
15WRX_STI_US_EN.book 118 ージ 20  
EN(STI)(diag)-119
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
W: DTC P0102 MASS OR VOLUME AIR FLOW CIRCUIT LOW INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-35, DTC P0102 MASS OR VOLUME AIR FLOW CIRCUIT
LOW INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Engine stalls.
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B83
456
123
*
B83
J/C
*
EN-10859
B3
123
4
5
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
B3
3
B550
216
10
B220
11
5
4
1
B135B:
B136C:
B30
C31
C11
C22
2
C10
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
*
MAIN RELAY
BATTERY
FUSE HOLDER
MASS AIR FLOW &
INTAKE AIR TEMPERATURE
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 119 ージ 20  
EN(STI)(diag)-120
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «Air Flow Sensor Volt-
age» using Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Air Flow Sensor
Voltage» less than 0.2 V?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK POWER SUPPLY OF MASS AIR
FLOW AND INTAKE AIR TEMPERATURE
SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the mass
air flow and intake air temperature sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between mass air flow
and intake air temperature sensor connector
and engine ground.
Connector & terminal
(B3) No. 3 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
main relay connec-
tor and mass air
flow and intake air
temperature sen-
sor connector
Poor contact of
main relay connec-
tor
3 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness between
ECM connector and the mass air flow and
intake air temperature sensor connector.
Connector & terminal
(B136) No. 22 — (B3) No. 5:
Is the resistance less than 1 Ω? Go to step 4. Repair the open
circuit of harness
between ECM con-
nector and the
mass air flow and
intake air tempera-
ture sensor con-
nector.
4 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 22 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the ground
short circuit of har-
ness between
ECM connector
and the mass air
flow and intake air
temperature sen-
sor connector.
5 CHECK FOR POOR CONTACT.
Check for poor contact of ECM and mass air
flow and intake air temperature sensor connec-
tor.
Is there poor contact of ECM or
mass air flow and intake air
temperature sensor connector?
Repair the poor
contact of ECM or
mass air flow and
intake air tempera-
ture sensor con-
nector.
Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
15WRX_STI_US_EN.book 120 ージ 20  
EN(STI)(diag)-121
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
X: DTC P0103 MASS OR VOLUME AIR FLOW CIRCUIT HIGH INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-36, DTC P0103 MASS OR VOLUME AIR FLOW CIRCUIT
HIGH INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Engine stalls.
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B83
456
123
*
B83
J/C
*
EN-10859
B3
123
4
5
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
B3
3
B550
216
10
B220
11
5
4
1
B135B:
B136C:
B30
C31
C11
C22
2
C10
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
*
MAIN RELAY
BATTERY
FUSE HOLDER
MASS AIR FLOW &
INTAKE AIR TEMPERATURE
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 121 ージ 20  
EN(STI)(diag)-122
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «Air Flow Sensor Volt-
age» using Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Air Flow Sensor
Voltage» 5 V or more?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the mass
air flow and intake air temperature sensor.
3) Start the engine.
4) Read the value of «Air Flow Sensor Volt-
age» using Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Air Flow Sensor
Voltage» 5 V or more?
Repair the short
circuit of harness
to power supply
between ECM con-
nector and the
mass air flow and
intake air tempera-
ture sensor con-
nector.
Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness between
mass air flow and intake air temperature sensor
connector and engine ground.
Connector & terminal
(B3) No. 4 — Engine ground:
Is the resistance less than 5 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and the mass air
flow and intake air
temperature sen-
sor connector
Poor contact of
ECM connector
4 CHECK FOR POOR CONTACT.
Check for poor contact of mass air flow and
intake air temperature sensor connector.
Is there poor contact of mass
air flow and intake air tempera-
ture sensor connector?
Repair the poor
contact of mass air
flow and intake air
temperature sen-
sor connector.
Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
15WRX_STI_US_EN.book 122 ージ 20  
EN(STI)(diag)-123
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Y: DTC P0107 MANIFOLD ABSOLUTE PRESSURE/BAROMETRIC PRESSURE
CIRCUIT LOW INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-37, DTC P0107 MANIFOLD ABSOLUTE PRESSURE/
BAROMETRIC PRESSURE CIRCUIT LOW INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B134A:
B137D:
E2B21
28
23
6
E21
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
1
2
3
A29
D20
A19
EN-10860
213
E21
ECM
MANIFOLD ABSOLUTE
PRESSURE SENSOR
15WRX_STI_US_EN.book 123 ージ 20  
EN(STI)(diag)-124
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «Mani. Absolute Pres-
sure» using the Subaru Select Monitor or a gen-
eral scan tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Mani. Absolute
Pressure» less than 13.3 kPa
(100 mmHg, 3.94 inHg)?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK POWER SUPPLY OF MANIFOLD
ABSOLUTE PRESSURE SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from manifold
absolute pressure sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between manifold
absolute pressure sensor connector and
engine ground.
Connector & terminal
(E21) No. 3 (+) — Engine ground (–):
Is the voltage 4.5 V or more? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and manifold abso-
lute pressure sen-
sor connector
Poor contact of
ECM connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness between
ECM connector and manifold absolute pressure
sensor connector.
Connector & terminal
(B137) No. 20 — (E21) No. 1:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and manifold abso-
lute pressure sen-
sor connector
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 20 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair short cir-
cuit to ground in
harness between
ECM connector
and manifold abso-
lute pressure sen-
sor connector.
5 CHECK FOR POOR CONTACT.
Check for poor contact of ECM and manifold
absolute pressure sensor connector.
Is there poor contact of ECM or
manifold absolute pressure
sensor connector?
Repair the poor
contact of ECM or
manifold absolute
pressure sensor
connector.
Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(STI)-41,
Manifold Absolute
Pressure Sensor.>
15WRX_STI_US_EN.book 124 ージ 20  
EN(STI)(diag)-125
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Z: DTC P0108 MANIFOLD ABSOLUTE PRESSURE/BAROMETRIC PRESSURE
CIRCUIT HIGH INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-38, DTC P0108 MANIFOLD ABSOLUTE PRESSURE/
BAROMETRIC PRESSURE CIRCUIT HIGH INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B134A:
B137D:
E2B21
28
23
6
E21
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
1
2
3
A29
D20
A19
EN-10860
213
E21
ECM
MANIFOLD ABSOLUTE
PRESSURE SENSOR
15WRX_STI_US_EN.book 125 ージ 20  
EN(STI)(diag)-126
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «Mani. Absolute Pres-
sure» using the Subaru Select Monitor or a gen-
eral scan tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Mani. Absolute
Pressure» 119.5 kPa (896.5
mmHg, 35.29 inHg) or more?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from manifold
absolute pressure sensor.
3) Start the engine.
4) Read the value of «Mani. Absolute Pres-
sure» using the Subaru Select Monitor or a gen-
eral scan tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Mani. Absolute
Pressure» 119.5 kPa (896.5
mmHg, 35.29 inHg) or more?
Repair the short
circuit to power in
harness between
ECM connector
and manifold abso-
lute pressure sen-
sor connector.
Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND
MANIFOLD ABSOLUTE PRESSURE SEN-
SOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness between
manifold absolute pressure sensor connector
and engine ground.
Connector & terminal
(E21) No. 2 — Engine ground:
Is the resistance less than 5 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and manifold abso-
lute pressure sen-
sor connector
Poor contact of
ECM connector
Poor contact of
coupling connector
4 CHECK FOR POOR CONTACT.
Check for poor contact of manifold absolute
pressure sensor connector.
Is there poor contact of mani-
fold absolute pressure sensor
connector?
Repair the poor
contact of mani-
fold absolute pres-
sure sensor
connector.
Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(STI)-41,
Manifold Absolute
Pressure Sensor.>
15WRX_STI_US_EN.book 126 ージ 20  
EN(STI)(diag)-127
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AA:DTC P0111 INTAKE AIR TEMPERATURE SENSOR RANGE/PERFORMANCE
PROBLEM
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-39, DTC P0111 INTAKE AIR TEMPERATURE SENSOR
RANGE/PERFORMANCE PROBLEM, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK CURRENT DATA.
1) Turn the ignition switch to ON.
2) Read the value of «Intake Air Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
3) Read the change of the value in «Intake Air
Temp.» while heating and cooling the mass air
flow and intake air temperature sensor using a
hair dryer.
CAUTION:
Do not heat the part to the temperature
where you cannot touch it with your bare
hand in order to prevent burning yourself
and protect the part.
Does the value of «Intake Air
Temp.» change between heat-
ing and cooling?
Repair the poor
contact of ECM
connector.
Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
15WRX_STI_US_EN.book 127 ージ 20  
EN(STI)(diag)-128
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AB:DTC P0112 INTAKE AIR TEMPERATURE SENSOR 1 CIRCUIT LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-42, DTC P0112 INTAKE AIR TEMPERATURE SENSOR 1
CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B83
456
123
*
B83
J/C
*
EN-10859
B3
123
4
5
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
B3
3
B550
216
10
B220
11
5
4
1
B135B:
B136C:
B30
C31
C11
C22
2
C10
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
*
MAIN RELAY
BATTERY
FUSE HOLDER
MASS AIR FLOW &
INTAKE AIR TEMPERATURE
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 128 ージ 20  
EN(STI)(diag)-129
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «Intake Air Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Intake Air
Temp.» 120°C (248°F) or
more?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
the mass air flow and intake air temperature
sensor.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 31 — Chassis ground:
Is the resistance 1 MΩ or
more?
Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
Repair the ground
short circuit of har-
ness between
ECM connector
and the mass air
flow and intake air
temperature sen-
sor connector.
15WRX_STI_US_EN.book 129 ージ 20  
EN(STI)(diag)-130
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AC:DTC P0113 INTAKE AIR TEMPERATURE SENSOR 1 CIRCUIT HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-43, DTC P0113 INTAKE AIR TEMPERATURE SENSOR 1
CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B83
456
123
*
B83
J/C
*
EN-10859
B3
123
4
5
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
B3
3
B550
216
10
B220
11
5
4
1
B135B:
B136C:
B30
C31
C11
C22
2
C10
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
*
MAIN RELAY
BATTERY
FUSE HOLDER
MASS AIR FLOW &
INTAKE AIR TEMPERATURE
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 130 ージ 20  
EN(STI)(diag)-131
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «Intake Air Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Intake Air Temp.»
less than –40°C (–40°F)?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK FOR POOR CONTACT.
Check for poor contact of ECM and mass air
flow and intake air temperature sensor connec-
tor.
Is there poor contact of ECM or
mass air flow and intake air
temperature sensor connector?
Repair the poor
contact of ECM or
mass air flow and
intake air tempera-
ture sensor con-
nector.
Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
the mass air flow and intake air temperature
sensor.
3) Measure the resistance of harness between
ECM connector and the mass air flow and
intake air temperature sensor connector.
Connector & terminal
(B136) No. 31 — (B3) No. 1:
(B135) No. 30 — (B3) No. 2:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and the mass air
flow and intake air
temperature sen-
sor connector
Poor contact of
joint connector
4 CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW AND INTAKE AIR TEM-
PERATURE SENSOR CONNECTOR.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 31 (+) — Chassis ground (–):
Is the voltage 5 V or more? Repair the short
circuit of harness
to power supply
between ECM con-
nector and the
mass air flow and
intake air tempera-
ture sensor con-
nector.
Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
15WRX_STI_US_EN.book 131 ージ 20  
EN(STI)(diag)-132
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AD:DTC P0116 ENGINE COOLANT TEMPERATURE SENSOR 1 CIRCUIT
RANGE/PERFORMANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-44, DTC P0116 ENGINE COOLANT TEMPERATURE SEN-
SOR 1 CIRCUIT RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Hard to start
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Disconnect the connectors from the engine
coolant temperature sensor.
2) Measure the resistance between engine
coolant temperature sensor terminals when the
engine coolant is cold and after warmed up.
Terminals
No. 1 — No. 2:
Is the resistance of engine cool-
ant temperature sensor differ-
ent between when engine
coolant is cold and after
warmed up?
Repair the poor
contact of ECM
connector.
Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(STI)-33,
Engine Coolant
Temperature Sen-
sor.>
15WRX_STI_US_EN.book 132 ージ 20  
EN(STI)(diag)-133
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AE:DTC P0117 ENGINE COOLANT TEMPERATURE CIRCUIT LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-46, DTC P0117 ENGINE COOLANT TEMPERATURE CIR-
CUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Hard to start
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
E8
12
B134A:
B137D:
E2B21
12
6
E8
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
1
2
A29
D22
EN-10171
ECM
ENGINE COOLANT
TEMPERATURE
SENSOR
15WRX_STI_US_EN.book 133 ージ 20  
EN(STI)(diag)-134
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «Coolant Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Coolant Temp.»
150°C (302°F) or more?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK HARNESS BETWEEN ECM AND EN-
GINE COOLANT TEMPERATURE SENSOR
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
engine coolant temperature sensor.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B137) No. 22 — Chassis ground:
Is the resistance 1 MΩ or
more?
Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(STI)-33,
Engine Coolant
Temperature Sen-
sor.>
Repair the short
circuit to ground in
harness between
ECM connector
and engine coolant
temperature sen-
sor connector.
15WRX_STI_US_EN.book 134 ージ 20  
EN(STI)(diag)-135
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AF:DTC P0118 ENGINE COOLANT TEMPERATURE CIRCUIT HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-47, DTC P0118 ENGINE COOLANT TEMPERATURE CIR-
CUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Hard to start
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
E8
12
B134A:
B137D:
E2B21
12
6
E8
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
1
2
A29
D22
EN-10171
ECM
ENGINE COOLANT
TEMPERATURE
SENSOR
15WRX_STI_US_EN.book 135 ージ 20  
EN(STI)(diag)-136
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «Coolant Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Coolant Temp.»
less than –40°C (–40°F)?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK FOR POOR CONTACT.
Check for poor contact of ECM and engine cool-
ant temperature sensor connector.
Is there poor contact of ECM or
engine coolant temperature
sensor connector?
Repair the poor
contact of ECM or
engine coolant
temperature sen-
sor connector.
Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND EN-
GINE COOLANT TEMPERATURE SENSOR
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
engine coolant temperature sensor.
3) Measure the resistance of harness between
ECM connector and engine coolant tempera-
ture sensor connector.
Connector & terminal
(B134) No. 29 — (E8) No. 1:
(B137) No. 22 — (E8) No. 2:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and engine coolant
temperature sen-
sor connector
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND EN-
GINE COOLANT TEMPERATURE SENSOR
CONNECTOR.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 22 (+) — Chassis ground (–):
Is the voltage 5 V or more? Repair the short
circuit of harness
to power supply
between ECM con-
nector and engine
coolant tempera-
ture sensor con-
nector.
Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(STI)-33,
Engine Coolant
Temperature Sen-
sor.>
15WRX_STI_US_EN.book 136 ージ 20  
EN(STI)(diag)-137
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AG:DTC P0122 THROTTLE/PEDAL POSITION SENSOR/SWITCH “A” CIRCUIT
LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-48, DTC P0122 THROTTLE/PEDAL POSITION SENSOR/
SWITCH “A” CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Engine stalls.
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 137 ージ 20  
EN(STI)(diag)-138
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
electronic throttle control.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 19 — Chassis ground:
(B134) No. 18 — Chassis ground:
(B134) No. 18 — (B136) No. 4:
Is the resistance 1 MΩ or
more?
Go to step 2. Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
28
36
35
40
34
A3
A6
D1
D3
A4
B225
14
17
15
16
B122
J/C
*
*
B550
216
418
B220
1011
E2
B21
25
39
38
6
24
E57
B134A:
B135B:
B136C:
B137D:
A1
A2
A29
A28
6
5
4
3
2
1
A19
A18
C4
B17
B7
B225B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
321654
E57
B122
34
56
12
78
EN-10861
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
ECM
SBF-7
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
*
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
ELECTRONIC THROTTLE
CONTROL
MAIN
RELAY
FUSE
HOLDER
ELECTRONIC THROTTLE
CONTROL RELAY
15WRX_STI_US_EN.book 138 ージ 20  
EN(STI)(diag)-139
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Connect the connector to ECM.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 6 — Engine ground:
Is the resistance 1 MΩ or
more?
Replace the elec-
tronic throttle con-
trol. <Ref. to
FU(STI)-15, Throt-
tle Body.>
Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
Replace the ECM if
defective. <Ref. to
FU(STI)-56,
Engine Control
Module (ECM).>
Step Check Yes No
15WRX_STI_US_EN.book 139 ージ 20  
EN(STI)(diag)-140
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AH:DTC P0123 THROTTLE/PEDAL POSITION SENSOR/SWITCH “A” CIRCUIT
HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-49, DTC P0123 THROTTLE/PEDAL POSITION SENSOR/
SWITCH “A” CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Engine stalls.
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 140 ージ 20  
EN(STI)(diag)-141
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
electronic throttle control.
3) Measure the resistance of harness between
ECM connector and electronic throttle control
connector.
Connector & terminal
(B134) No. 18 — (E57) No. 6:
(B134) No. 29 — (E57) No. 3:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and electronic
throttle control
connector
Poor contact of
coupling connector
28
36
35
40
34
A3
A6
D1
D3
A4
B225
14
17
15
16
B122
J/C
*
*
B550
216
418
B220
1011
E2
B21
25
39
38
6
24
E57
B134A:
B135B:
B136C:
B137D:
A1
A2
A29
A28
6
5
4
3
2
1
A19
A18
C4
B17
B7
B225B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
321654
E57
B122
34
56
12
78
EN-10861
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
ECM
SBF-7
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
*
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
ELECTRONIC THROTTLE
CONTROL
MAIN
RELAY
FUSE
HOLDER
ELECTRONIC THROTTLE
CONTROL RELAY
15WRX_STI_US_EN.book 141 ージ 20  
EN(STI)(diag)-142
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Connect the connector to ECM.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 3 — Engine ground:
Is the resistance less than 5 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
ECM connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 6 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
Go to step 4.
4 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B134) No. 19 — (B134) No. 18:
Is the resistance 1 MΩ or
more?
Repair the poor
contact of elec-
tronic throttle con-
trol connector.
Replace the elec-
tronic throttle con-
trol if defective.
<Ref. to FU(STI)-
15, Throttle Body.>
Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
Step Check Yes No
15WRX_STI_US_EN.book 142 ージ 20  
EN(STI)(diag)-143
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AI: DTC P0125 INSUFFICIENT COOLANT TEMPERATURE FOR CLOSED LOOP
FUEL CONTROL
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-50, DTC P0125 INSUFFICIENT COOLANT TEMPERA-
TURE FOR CLOSED LOOP FUEL CONTROL, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine does not return to idle.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK TIRE SIZE. Is the tire size as specified and
the same size as three other
wheels?
Go to step 2. Replace the tire.
2 CHECK ENGINE COOLANT.
Check the following items:
Amount of engine coolant
Engine coolant freeze
Contamination of engine coolant
Is the engine coolant normal? Go to step 3. Fill or replace the
engine coolant.
<Ref. to CO(STI)-
13, Engine Cool-
ant.>
3 CHECK THERMOSTAT. Does the thermostat remain
opened?
Replace the ther-
mostat. <Ref. to
CO(STI)-17, Ther-
mostat.>
Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(STI)-33,
Engine Coolant
Temperature Sen-
sor.>
15WRX_STI_US_EN.book 143 ージ 20  
EN(STI)(diag)-144
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AJ:DTC P0128 COOLANT THERMOSTAT (ENGINE COOLANT TEMPERATURE
BELOW THERMOSTAT REGULATING TEMPERATURE)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-52, DTC P0128 COOLANT THERMOSTAT (ENGINE
COOLANT TEMPERATURE BELOW THERMOSTAT REGULATING TEMPERATURE), Diagnostic Trouble
Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Thermostat remains open.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK ENGINE COOLANT. Is the engine coolant amount
normal?
Go to step 3. Refill the engine
coolant. <Ref. to
CO(STI)-13,
Engine Coolant.>
3 CHECK RADIATOR FAN.
1) Start the engine.
2) Check the radiator fan operation.
Does the radiator fan continu-
ously rotate for 3 minutes or
more during idling?
Repair radiator fan
circuit. <Ref. to
CO(STI)-23, Radi-
ator Main Fan and
Fan Motor.> <Ref.
to CO(STI)-25,
Radiator Sub Fan
and Fan Motor.>
Replace the ther-
mostat. <Ref. to
CO(STI)-17, Ther-
mostat.>
15WRX_STI_US_EN.book 144 ージ 20  
EN(STI)(diag)-145
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AK:DTC P0131 O2 SENSOR CIRCUIT LOW VOLTAGE (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-56, DTC P0131 O2 SENSOR CIRCUIT LOW VOLTAGE
(BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 145 ージ 20  
EN(STI)(diag)-146
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 18 — Chassis ground:
(B136) No. 19 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and front oxygen
(A/F) sensor con-
nector.
3 CHECK FOR POOR CONTACT.
Check for poor contact of the front oxygen (A/F)
sensor connector.
Is there poor contact of front
oxygen (A/F) sensor connec-
tor?
Repair the poor
contact of front
oxygen (A/F) sen-
sor connector.
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
15WRX_STI_US_EN.book 146 ージ 20  
EN(STI)(diag)-147
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AL:DTC P0132 O2 SENSOR CIRCUIT HIGH VOLTAGE (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-57, DTC P0132 O2 SENSOR CIRCUIT HIGH VOLTAGE
(BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 147 ージ 20  
EN(STI)(diag)-148
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from front oxy-
gen (A/F) sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 18 (+) — Chassis ground (–):
(B136) No. 19 (+) — Chassis ground (–):
Is the voltage 8 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
15WRX_STI_US_EN.book 148 ージ 20  
EN(STI)(diag)-149
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AM:DTC P0134 O2 SENSOR CIRCUIT NO ACTIVITY DETECTED (BANK 1 SEN-
SOR 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-58, DTC P0134 O2 SENSOR CIRCUIT NO ACTIVITY DE-
TECTED (BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 149 ージ 20  
EN(STI)(diag)-150
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
3) Measure the resistance of harness between
ECM connector and front oxygen (A/F) sensor
connector.
Connector & terminal
(B136) No. 18 — (B379) No. 3:
(B136) No. 19 — (B379) No. 4:
Is the resistance less than 1 Ω? Go to step 2. Repair the open
circuit of harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
2 CHECK FOR POOR CONTACT.
Check for poor contact of ECM and front oxygen
(A/F) sensor connector.
Is there poor contact of ECM or
front oxygen (A/F) sensor con-
nector?
Repair the poor
contact of ECM or
front oxygen (A/F)
sensor connector.
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
15WRX_STI_US_EN.book 150 ージ 20  
EN(STI)(diag)-151
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AN:DTC P0137 O2 SENSOR CIRCUIT LOW VOLTAGE (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-59, DTC P0137 O2 SENSOR CIRCUIT LOW VOLTAGE
(BANK 1 SENSOR 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 151 ージ 20  
EN(STI)(diag)-152
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), and
keep the engine speed at 3,000 rpm. (2 minutes
maximum)
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Rear O2 Sen-
sor» 0.490 V or more?
Go to step 5. Go to step 2.
2 CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM connector and rear oxygen sensor con-
nector.
Connector & terminal
(B136) No. 20 — (T6) No. 3:
(B135) No. 30 — (T6) No. 4:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(T6) No. 3 (+) — Chassis ground (–):
Is the voltage 0.2 — 0.5 V? Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
ECM connector
Poor contact of
coupling connector
5 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following items.
Looseness and improper fitting of exhaust
system parts
Damage (crack, hole etc.) of parts
Loose part and improper installation between
front oxygen (A/F) sensor and rear oxygen sen-
sor
Is there any fault in exhaust
system?
Repair or replace
faulty parts.
Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
15WRX_STI_US_EN.book 152 ージ 20  
EN(STI)(diag)-153
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AO:DTC P0138 O2 SENSOR CIRCUIT HIGH VOLTAGE (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-60, DTC P0138 O2 SENSOR CIRCUIT HIGH VOLTAGE
(BANK 1 SENSOR 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 153 ージ 20  
EN(STI)(diag)-154
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), and
rapidly reduce the engine speed from 3,000
rpm.
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“Current Data Display For Engine”. <Ref. to
EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Rear O2 Sen-
sor» 0.250 V or less?
Go to step 5. Go to step 2.
2 CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM connector and rear oxygen sensor con-
nector.
Connector & terminal
(B136) No. 20 — (T6) No. 3:
(B135) No. 30 — (T6) No. 4:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(T6) No. 3 (+) — Chassis ground (–):
Is the voltage 0.2 — 0.5 V? Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
ECM connector
Poor contact of
coupling connector
5 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following items.
Looseness and improper fitting of exhaust
system parts
Damage (crack, hole etc.) of parts
Loose part and improper installation between
front oxygen (A/F) sensor and rear oxygen sen-
sor
Is there any fault in exhaust
system?
Repair or replace
faulty parts.
Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
15WRX_STI_US_EN.book 154 ージ 20  
EN(STI)(diag)-155
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AP:DTC P013A O2 SENSOR SLOW RESPONSE - RICH TO LEAN (BANK 1 SEN-
SOR 2)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-61, DTC P013A O2 SENSOR SLOW RESPONSE - RICH
TO LEAN (BANK 1 SENSOR 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 155 ージ 20  
EN(STI)(diag)-156
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM connector and rear oxygen sensor con-
nector.
Connector & terminal
(B136) No. 20 — (T6) No. 3:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
Measure the resistance between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(T6) No. 3 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and rear oxygen
sensor connector.
3 CHECK REAR OXYGEN SENSOR.
Measure the resistance between rear oxygen
sensor terminals.
Terminals
No. 3 — No. 4
Is the resistance less than 1 Ω? Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
15WRX_STI_US_EN.book 156 ージ 20  
EN(STI)(diag)-157
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AQ:DTC P013B O2 SENSOR SLOW RESPONSE - LEAN TO RICH (BANK 1 SEN-
SOR 2)
NOTE:
For the diagnostic procedure, refer to DTC P013A. <Ref. to EN(STI)(diag)-155, DTC P013A O2 SENSOR
SLOW RESPONSE - RICH TO LEAN (BANK 1 SENSOR 2), Diagnostic Procedure with Diagnostic Trouble
Code (DTC).>
AR:DTC P013E O2 SENSOR DELAYED RESPONSE - RICH TO LEAN (BANK 1
SENSOR 2)
NOTE:
For the diagnostic procedure, refer to DTC P013A. <Ref. to EN(STI)(diag)-155, DTC P013A O2 SENSOR
SLOW RESPONSE - RICH TO LEAN (BANK 1 SENSOR 2), Diagnostic Procedure with Diagnostic Trouble
Code (DTC).>
AS:DTC P013F O2 SENSOR DELAYED RESPONSE - LEAN TO RICH (BANK 1
SENSOR 2)
NOTE:
For the diagnostic procedure, refer to DTC P013A. <Ref. to EN(STI)(diag)-155, DTC P013A O2 SENSOR
SLOW RESPONSE - RICH TO LEAN (BANK 1 SENSOR 2), Diagnostic Procedure with Diagnostic Trouble
Code (DTC).>
AT:DTC P0141 O2 SENSOR HEATER CIRCUIT (BANK1 SENSOR2)
NOTE:
For the diagnostic procedure, refer to DTC P0037. <Ref. to EN(STI)(diag)-111, DTC P0037 HO2S HEATER
CONTROL CIRCUIT LOW (BANK 1 SENSOR 2), Diagnostic Procedure with Diagnostic Trouble Code
(DTC).>
15WRX_STI_US_EN.book 157 ージ 20  
EN(STI)(diag)-158
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AU:DTC P014C O2 SENSOR SLOW RESPONSE - RICH TO LEAN (BANK 1 SEN-
SOR 1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-70, DTC P014C O2 SENSOR SLOW RESPONSE - RICH
TO LEAN (BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
AV:DTC P014D O2 SENSOR SLOW RESPONSE - LEAN TO RICH (BANK 1 SEN-
SOR 1)
NOTE:
For the diagnostic procedure, refer to DTC P014C. <Ref. to EN(STI)(diag)-158, DTC P014C O2 SENSOR
SLOW RESPONSE - RICH TO LEAN (BANK 1 SENSOR 1), Diagnostic Procedure with Diagnostic Trouble
Code (DTC).>
AW:DTC P015A O2 SENSOR DELAYED RESPONSE - RICH TO LEAN (BANK 1
SENSOR 1)
NOTE:
For the diagnostic procedure, refer to DTC P014C. <Ref. to EN(STI)(diag)-158, DTC P014C O2 SENSOR
SLOW RESPONSE - RICH TO LEAN (BANK 1 SENSOR 1), Diagnostic Procedure with Diagnostic Trouble
Code (DTC).>
AX:DTC P015B O2 SENSOR DELAYED RESPONSE - LEAN TO RICH (BANK 1
SENSOR 1)
NOTE:
For the diagnostic procedure, refer to DTC P014C. <Ref. to EN(STI)(diag)-158, DTC P014C O2 SENSOR
SLOW RESPONSE - RICH TO LEAN (BANK 1 SENSOR 1), Diagnostic Procedure with Diagnostic Trouble
Code (DTC).>
AY:DTC P0171 SYSTEM TOO LEAN (BANK 1)
NOTE:
For the diagnostic procedure, refer to DTC P0172. <Ref. to EN(STI)(diag)-159, DTC P0172 SYSTEM TOO
RICH (BANK 1), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
Step Check Yes No
1 CHECK EXHAUST SYSTEM.
NOTE:
Check the following items.
Loose installation of front portion of exhaust
pipe onto cylinder heads
Loose connection between front exhaust pipe
and front catalytic converter
Damage of exhaust pipe resulting in a hole
Is there any fault in exhaust
system?
Repair the exhaust
system.
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
15WRX_STI_US_EN.book 158 ージ 20  
EN(STI)(diag)-159
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
AZ:DTC P0172 SYSTEM TOO RICH (BANK 1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-79, DTC P0172 SYSTEM TOO RICH (BANK 1), Diagnostic
Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Engine stalls.
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK EXHAUST SYSTEM. Are there holes or loose bolts
on exhaust system?
Repair the exhaust
system.
Go to step 2.
2 CHECK AIR INTAKE SYSTEM. Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
Go to step 3.
3 CHECK FUEL PRESSURE.
WARNING:
Place “NO OPEN FLAMES” signs near the
working area.
CAUTION:
Be careful not to spill fuel.
Measure the fuel pressure while disconnecting
pressure regulator vacuum hose from intake
manifold. <Ref. to ME(STI)-25, INSPECTION,
Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze the
fuel return hose 2 to 3 times, then measure fuel
pressure again.
Is the measured value 284 —
314 kPa (2.9 — 3.2 kg/cm
2
, 41
— 46 psi)?
Go to step 4. Check the fuel
pump and fuel
delivery line. <Ref.
to FU(STI)-83,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-99,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
4 CHECK FUEL PRESSURE.
After connecting the pressure regulator vacuum
hose, measure fuel pressure. <Ref. to ME(STI)-
25, INSPECTION, Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure fuel
pressure again.
If the measured value at this step is out of
specification, check or replace pressure regula-
tor and pressure regulator vacuum hose.
Is the measured value 230 —
260 kPa (2.4 — 2.7 kg/cm
2
, 33
— 38 psi)?
Go to step 5. Check the fuel
pump and fuel
delivery line. <Ref.
to FU(STI)-83,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-99,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
15WRX_STI_US_EN.book 159 ージ 20  
EN(STI)(diag)-160
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
5 CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm up completely.
2) Read the value of «Coolant Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Coolant Temp.»
75°C (167°F) or more?
Go to step 6. Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(STI)-33,
Engine Coolant
Temperature Sen-
sor.>
6 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Read the value of «Mass Air Flow» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Mass Air
Flow» 2.0 — 5.0 g/s (0.26 —
0.66 lb/m)?
Go to step 7. Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
7 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Open the front hood.
6) Measure the ambient temperature.
7) Read the value of «Intake Air Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Subtract ambient temperature
from «Intake Air Temp.». Is the
obtained value –10 — 50°C (–18
— 90°F)?
Repair the poor
contact of ECM
connector.
Check the mass air
flow and intake air
temperature sen-
sor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
Step Check Yes No
15WRX_STI_US_EN.book 160 ージ 20  
EN(STI)(diag)-161
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BA:DTC P0201 INJECTOR #1
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-80, DTC P0201 INJECTOR #1, Diagnostic Trouble Code
(DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
10
B220
11
B550
216
51
52
53
54
E2
B21
48
2
1
E5
B134
10
11
12
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B134
8
5
6
10 11 12 13 14 15
72134
16
30
19 20 22
28 29
9
17
18 2521 23 24
3231
26 27
33 34
EN-10855
2
1
E16
2
1
E6
2
1
E17
13
E5
E6
E16
E17
21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
FUEL INJECTOR No. 4
FUEL INJECTOR No. 3
FUEL INJECTOR No. 2
FUEL INJECTOR No. 1
BATTERY
FUSE HOLDER
MAIN RELAY
15WRX_STI_US_EN.book 161 ージ 20  
EN(STI)(diag)-162
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK POWER SUPPLY TO FUEL INJEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector.
3) Turn the ignition switch to ON.
4) Measure the voltage between fuel injector
connector and the engine ground.
Connector & terminal
DTC P0201; (E5) No. 1 (+) — Engine
ground (–):
DTC P0202; (E16) No. 1 (+) — Engine
ground (–):
DTC P0203; (E6) No. 1 (+) — Engine
ground (–):
DTC P0204; (E17) No. 1 (+) — Engine
ground (–):
Is the voltage 10 V or more? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
main relay and fuel
injector connector
Poor contact of
main relay connec-
tor
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between fuel injec-
tor connector and engine ground.
Connector & terminal
DTC P0201; (E5) No. 2 — Engine ground:
DTC P0202; (E16) No. 2 — Engine ground:
DTC P0203; (E6) No. 2 — Engine ground:
DTC P0204; (E17) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and fuel injector
connector.
3 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
Measure the resistance of harness between
ECM connector and fuel injector connector.
Connector & terminal
DTC P0201; (B134) No. 10 — (E5) No. 2:
DTC P0202; (B134) No. 11 — (E16) No. 2:
DTC P0203; (B134) No. 12 — (E6) No. 2:
DTC P0204; (B134) No. 13 — (E17) No. 2:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and fuel injector
connector
Poor contact of
coupling connector
4 CHECK FUEL INJECTOR.
Measure the resistance between fuel injector
terminals on the corresponding cylinder.
Terminals
No. 1 — No. 2:
Is the resistance 5 — 20 Ω? Go to step 5. Replace the fuel
injector. <Ref. to
FU(STI)-43, Fuel
Injector.>
5 CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.
Is there poor contact of ECM
connector?
Repair the poor
contact of ECM
connector.
Go to step 6.
15WRX_STI_US_EN.book 162 ージ 20  
EN(STI)(diag)-163
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BB:DTC P0202 INJECTOR #2
NOTE:
For the diagnostic procedure, refer to DTC P0201. <Ref. to EN(STI)(diag)-161, DTC P0201 INJECTOR #1,
Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
BC:DTC P0203 INJECTOR #3
NOTE:
For the diagnostic procedure, refer to DTC P0201. <Ref. to EN(STI)(diag)-161, DTC P0201 INJECTOR #1,
Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
BD:DTC P0204 INJECTOR #4
NOTE:
For the diagnostic procedure, refer to DTC P0201. <Ref. to EN(STI)(diag)-161, DTC P0201 INJECTOR #1,
Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
6 CHECK FUEL INJECTOR OPERATION.
1) Connect all connectors.
2) Start the engine.
3) Check if the corresponding fuel injector
emits operating sound.
NOTE:
Use a sound scope to check the operating
sound.
Does the fuel injector emit
operating sound?
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
Repair the poor
contact of fuel
injector connector.
Step Check Yes No
15WRX_STI_US_EN.book 163 ージ 20  
EN(STI)(diag)-164
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BE:DTC P0222 THROTTLE/PEDAL POSITION SENSOR/SWITCH “B” CIRCUIT
LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-81, DTC P0222 THROTTLE/PEDAL POSITION SENSOR/
SWITCH “B” CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
Engine stalls.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
15WRX_STI_US_EN.book 164 ージ 20  
EN(STI)(diag)-165
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
electronic throttle control.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 19 — Chassis ground:
(B134) No. 28 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 2. Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
28
36
35
40
34
A3
A6
D1
D3
A4
B225
14
17
15
16
B122
J/C
*
*
B550
216
418
B220
1011
E2
B21
25
39
38
6
24
E57
B134A:
B135B:
B136C:
B137D:
A1
A2
A29
A28
6
5
4
3
2
1
A19
A18
C4
B17
B7
B225B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
321654
E57
B122
34
56
12
78
EN-10861
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
ECM
SBF-7
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
*
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
ELECTRONIC THROTTLE
CONTROL
MAIN
RELAY
FUSE
HOLDER
ELECTRONIC THROTTLE
CONTROL RELAY
15WRX_STI_US_EN.book 165 ージ 20  
EN(STI)(diag)-166
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Connect the connector to ECM.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 4 — Engine ground:
Is the resistance 1 MΩ or
more?
Replace the elec-
tronic throttle con-
trol. <Ref. to
FU(STI)-15, Throt-
tle Body.>
Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
Replace the ECM if
defective. <Ref. to
FU(STI)-56,
Engine Control
Module (ECM).>
Step Check Yes No
15WRX_STI_US_EN.book 166 ージ 20  
EN(STI)(diag)-167
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BF:DTC P0223 THROTTLE/PEDAL POSITION SENSOR/SWITCH “B” CIRCUIT
HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-82, DTC P0223 THROTTLE/PEDAL POSITION SENSOR/
SWITCH “B” CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
Engine stalls.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 167 ージ 20  
EN(STI)(diag)-168
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
electronic throttle control.
3) Measure the resistance of harness between
ECM connector and electronic throttle control
connector.
Connector & terminal
(B134) No. 28 — (E57) No. 4:
(B134) No. 29 — (E57) No. 3:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and electronic
throttle control
connector
Poor contact of
coupling connector
28
36
35
40
34
A3
A6
D1
D3
A4
B225
14
17
15
16
B122
J/C
*
*
B550
216
418
B220
1011
E2
B21
25
39
38
6
24
E57
B134A:
B135B:
B136C:
B137D:
A1
A2
A29
A28
6
5
4
3
2
1
A19
A18
C4
B17
B7
B225B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
321654
E57
B122
34
56
12
78
EN-10861
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
ECM
SBF-7
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
*
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
ELECTRONIC THROTTLE
CONTROL
MAIN
RELAY
FUSE
HOLDER
ELECTRONIC THROTTLE
CONTROL RELAY
15WRX_STI_US_EN.book 168 ージ 20  
EN(STI)(diag)-169
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Connect the connector to ECM.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 3 — Engine ground:
Is the resistance less than 5 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
ECM connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 4 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
Go to step 4.
4 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B134) No. 19 — (B134) No. 28:
Is the resistance 1 MΩ or
more?
Repair the poor
contact of elec-
tronic throttle con-
trol connector.
Replace the elec-
tronic throttle con-
trol if defective.
<Ref. to FU(STI)-
15, Throttle Body.>
Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
Step Check Yes No
15WRX_STI_US_EN.book 169 ージ 20  
EN(STI)(diag)-170
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BG:DTC P0230 FUEL PUMP PRIMARY CIRCUIT
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-83, DTC P0230 FUEL PUMP PRIMARY CIRCUIT, Diagnos-
tic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
12
34
56
R58
12
34
56789
10
R122
B135B
B136C
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
B97
1234 56789
10 11 12 13 14 15 16 17 18 19 20
EN-10862
R58
6
5
6
7
5
B97
R1
B220
21
10
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
R122
7
8
9
5
6
C33
B10
ECM
:
:
FUEL PUMP CU
BATTERY
FUEL PUMP RELAY
M/B No. 11
FUEL PUMP
15WRX_STI_US_EN.book 170 ージ 20  
EN(STI)(diag)-171
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK POWER SUPPLY CIRCUIT TO FUEL
PUMP CONTROL UNIT.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel pump
control unit.
3) Turn the ignition switch to ON.
4) Measure the voltage between fuel pump
control unit connector and chassis ground.
Connector & terminal
(R122) No. 10 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 2. Repair the power
supply circuit.
NOTE:
In this case, repair
the following item:
Open circuit or
short circuit to
ground in harness
between fuel pump
relay connector
and fuel pump con-
trol unit connector
Poor contact of
fuel pump relay
connector
Poor contact of
coupling connector
2 CHECK GROUND CIRCUIT OF FUEL PUMP
CONTROL UNIT.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness between
fuel pump control unit connector and chassis
ground.
Connector & terminal
(R122) No. 5 — Chassis ground:
Is the resistance less than 5 Ω? Go to step 3. Repair the open
circuit in harness
between fuel pump
control unit con-
nector and chassis
ground.
3 CHECK HARNESS BETWEEN FUEL PUMP
CONTROL UNIT AND FUEL PUMP CONNEC-
TOR.
1) Disconnect the connector from fuel pump.
2) Measure the resistance of harness between
fuel pump control unit and fuel pump connector.
Connector & terminal
(R122) No. 7 — (R58) No. 5:
(R122) No. 6 — (R58) No. 6:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
fuel pump control
unit connector and
fuel pump connec-
tor
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN FUEL PUMP
CONTROL UNIT AND FUEL PUMP CONNEC-
TOR.
Measure the resistance between fuel pump
control unit connector and chassis ground.
Connector & terminal
(R122) No. 7 — Chassis ground:
(R122) No. 6 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
fuel pump control
unit connector and
fuel pump connec-
tor.
5 CHECK HARNESS BETWEEN ECM AND
FUEL PUMP CONTROL UNIT CONNECTOR.
1) Disconnect the connector from ECM.
2) Measure the resistance of harness between
ECM connector and fuel pump control unit con-
nector.
Connector & terminal
(B135) No. 10 — (R122) No. 9:
(B136) No. 33 — (R122) No. 8:
Is the resistance less than 1 Ω? Go to step 6. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and fuel pump con-
trol unit connector
Poor contact of
coupling connector
15WRX_STI_US_EN.book 171 ージ 20  
EN(STI)(diag)-172
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
6 CHECK HARNESS BETWEEN ECM AND
FUEL PUMP CONTROL UNIT CONNECTOR.
Measure the resistance between fuel pump
control unit connector and chassis ground.
Connector & terminal
(R122) No. 9 — Chassis ground:
(R122) No. 8 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 7. Repair the short
circuit to ground in
harness between
ECM connector
and fuel pump con-
trol unit connector.
7 CHECK FOR POOR CONTACT.
Check for poor contact of ECM and fuel pump
control unit connector.
Is there poor contact of ECM or
fuel pump control unit connec-
tor?
Repair the poor
contact of ECM or
fuel pump control
unit connector.
Go to step 8.
8 CHECK EXPERIENCE OF RUNNING OUT OF
FUEL.
Has the vehicle experienced
running out of fuel?
Finish the diagno-
sis.
NOTE:
DTC may be re-
corded as a result
of fuel pump idling
while running out
of fuel.
Replace the fuel
pump control unit.
<Ref. to FU(STI)-
63, Fuel Pump
Control Unit.>
Step Check Yes No
15WRX_STI_US_EN.book 172 ージ 20  
EN(STI)(diag)-173
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BH:DTC P0244 TURBO/SUPER CHARGER WASTEGATE SOLENOID “A”
RANGE/PERFORMANCE
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-84, DTC P0244 TURBO/SUPER CHARGER WASTEGATE
SOLENOID “A” RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK WASTEGATE ACTUATOR PIPING
AND WASTEGATE CONTROL SOLENOID
VALVE PIPING.
Are there any damage or dis-
connection of hose in waste-
gate actuator piping or
wastegate control solenoid
valve piping?
Connect the
wastegate actuator
pipe or wastegate
control solenoid
valve pipe properly.
If defective,
replace the hose.
Replace the waste-
gate control sole-
noid valve. <Ref. to
FU(STI)-50,
Wastegate Control
Solenoid Valve.>
15WRX_STI_US_EN.book 173 ージ 20  
EN(STI)(diag)-174
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BI: DTC P0245 TURBO/SUPER CHARGER WASTEGATE SOLENOID “A” LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-85, DTC P0245 TURBO/SUPER CHARGER WASTEGATE
SOLENOID “A” LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK OUTPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 33 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 2. Go to step 3.
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
E2B21
50
48
EN-10863
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
01
B220
11
1
2
B134
33
E64
12
E64
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
WASTEGATE CONTROL
SOLENOID VALVE
MAIN RELAY
BATTERY
FUSE HOLDER
15WRX_STI_US_EN.book 174 ージ 20  
EN(STI)(diag)-175
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.
Is there poor contact of ECM
connector?
Repair the poor
contact of ECM
connector.
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary open or
short circuit of har-
ness or temporary
poor contact of
connector may be
the cause.
3 CHECK POWER SUPPLY TO WASTEGATE
CONTROL SOLENOID VALVE.
Measure the voltage between wastegate con-
trol solenoid valve connector and engine
ground.
Connector & terminal
(E64) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 4. Repair the power
supply circuit.
4 CHECK HARNESS BETWEEN ECM AND
WASTEGATE CONTROL SOLENOID VALVE
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
wastegate control solenoid valve.
3) Measure the resistance between wastegate
control solenoid valve connector and engine
ground.
Connector & terminal
(E64) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair ground
short circuit of har-
ness between
ECM connector
and wastegate
control solenoid
valve connector.
5 CHECK HARNESS BETWEEN ECM AND
WASTEGATE CONTROL SOLENOID VALVE
CONNECTOR.
Measure the resistance of harness between
ECM connector and wastegate control solenoid
valve connector.
Connector & terminal
(B134) No. 33 — (E64) No. 2:
Is the resistance less than 1 Ω? Go to step 6. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and wastegate
control solenoid
valve connector
Poor contact of
coupling connector
6 CHECK WASTEGATE CONTROL SOLE-
NOID VALVE.
1) Remove the wastegate control solenoid
valve.
2) Measure the resistance between wastegate
control solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance 10 — 100 Ω? Repair poor con-
tact of wastegate
control solenoid
valve connector.
Replace the waste-
gate control sole-
noid valve. <Ref. to
FU(STI)-50,
Wastegate Control
Solenoid Valve.>
Step Check Yes No
15WRX_STI_US_EN.book 175 ージ 20  
EN(STI)(diag)-176
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BJ:DTC P0246 TURBO/SUPER CHARGER WASTEGATE SOLENOID “A” HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-86, DTC P0246 TURBO/SUPER CHARGER WASTEGATE
SOLENOID “A” HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
WASTEGATE CONTROL SOLENOID VALVE
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
wastegate control solenoid valve.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 33 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair short cir-
cuit to power in
harness between
ECM connector
and wastegate
control solenoid
valve connector.
Go to step 2.
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
E2B21
50
48
EN-10863
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
01
B220
11
1
2
B134
33
E64
12
E64
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
WASTEGATE CONTROL
SOLENOID VALVE
MAIN RELAY
BATTERY
FUSE HOLDER
15WRX_STI_US_EN.book 176 ージ 20  
EN(STI)(diag)-177
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK WASTEGATE CONTROL SOLE-
NOID VALVE.
1) Turn the ignition switch to OFF.
2) Measure the resistance between wastegate
control solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance less than 1 Ω? Replace the waste-
gate control sole-
noid valve. <Ref. to
FU(STI)-50,
Wastegate Control
Solenoid Valve.>
Repair the poor
contact of ECM
connector.
Step Check Yes No
15WRX_STI_US_EN.book 177 ージ 20  
EN(STI)(diag)-178
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BK:DTC P0300 RANDOM/MULTIPLE CYLINDER MISFIRE DETECTED
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
Immediately at fault recognition (A misfire which could damage catalyst occurs.)
GENERAL DESCRIPTION <Ref. to GD(STI)-86, DTC P0300 RANDOM/MULTIPLE CYLINDER MISFIRE
DETECTED, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
Rough driving
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 178 ージ 20  
EN(STI)(diag)-179
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK OUTPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground on all cylinders.
Connector & terminal
#1 (B134) No. 10 (+) — Chassis ground (–):
#2 (B134) No. 11 (+) — Chassis ground (–):
#3 (B134) No. 12 (+) — Chassis ground (–):
#4 (B134) No. 13 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 6. Go to step 2.
10
B220
11
B550
216
51
52
53
54
E2
B21
48
2
1
E5
B134
10
11
12
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B134
8
5
6
10 11 12 13 14 15
72134
16
30
19 20 22
28 29
9
17
18 2521 23 24
3231
26 27
33 34
EN-10855
2
1
E16
2
1
E6
2
1
E17
13
E5
E6
E16
E17
21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
FUEL INJECTOR No. 4
FUEL INJECTOR No. 3
FUEL INJECTOR No. 2
FUEL INJECTOR No. 1
BATTERY
FUSE HOLDER
MAIN RELAY
15WRX_STI_US_EN.book 179 ージ 20  
EN(STI)(diag)-180
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from all fuel injec-
tors.
3) Measure the resistance between all fuel
injector connectors and engine ground.
Connector & terminal
#1 (E5) No. 2 — Engine ground:
#2 (E16) No. 2 — Engine ground:
#3 (E6) No. 2 — Engine ground:
#4 (E17) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and fuel injector
connector.
3 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
Measure the resistance of harness between
ECM connector and fuel injector connector on
all cylinders.
Connector & terminal
#1 (B134) No. 10 — (E5) No. 2:
#2 (B134) No. 11 — (E16) No. 2:
#3 (B134) No. 12 — (E6) No. 2:
#4 (B134) No. 13 — (E17) No. 2:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and fuel injector
connector
Poor contact of
coupling connector
4 CHECK FUEL INJECTOR.
Measure the resistance between all fuel injector
terminals.
Terminals
No. 1 — No. 2:
Is the resistance 5 — 20 Ω? Go to step 5. Replace the faulty
fuel injector. <Ref.
to FU(STI)-43,
Fuel Injector.>
5 CHECK POWER SUPPLY LINE.
1) Turn the ignition switch to ON.
2) Measure the voltage between all fuel injec-
tor connectors and the engine ground.
Connector & terminal
#1 (E5) No. 1 (+) — Engine ground (–):
#2 (E16) No. 1 (+) — Engine ground (–):
#3 (E6) No. 1 (+) — Engine ground (–):
#4 (E17) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Repair the poor
contact of all con-
nectors in fuel
injector circuit.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
the main relay con-
nector and fuel in-
jector connector on
faulty cylinders
Poor contact of
coupling connector
Poor contact of
main relay connec-
tor
6 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from all fuel injec-
tors.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground on all cylinders.
Connector & terminal
#1 (B134) No. 10 (+) — Chassis ground (–):
#2 (B134) No. 11 (+) — Chassis ground (–):
#3 (B134) No. 12 (+) — Chassis ground (–):
#4 (B134) No. 13 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and fuel injector
connectors.
Go to step 7.
Step Check Yes No
15WRX_STI_US_EN.book 180 ージ 20  
EN(STI)(diag)-181
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
7 CHECK FUEL INJECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between all fuel
injector terminals.
Terminals
No. 1 — No. 2:
Is the resistance 5 — 20 Ω? Go to step 8. Replace the faulty
fuel injector. <Ref.
to FU(STI)-43,
Fuel Injector.>
8 CHECK INSTALLATION OF CAMSHAFT PO-
SITION SENSOR/CRANKSHAFT POSITION
SENSOR.
Is the camshaft position sensor
or crankshaft position sensor
loosely installed?
Tighten the cam-
shaft position sen-
sor or crankshaft
position sensor.
<Ref. to FU(STI)-
35, Camshaft Posi-
tion Sensor.> <Ref.
to FU(STI)-34,
Crankshaft Posi-
tion Sensor.>
Go to step 9.
9 CHECK CRANK SPROCKET.
Remove the timing belt cover.
Is the crank sprocket rusted or
does it have broken teeth?
Replace the crank
sprocket. <Ref. to
ME(STI)-61, Crank
Sprocket.>
Go to step 10.
10 CHECK INSTALLATION CONDITION OF
TIMING BELT.
Turn the crankshaft, and align alignment mark
on crank sprocket with alignment mark on cylin-
der block.
ST 499987500 CRANKSHAFT
SOCKET
Is the timing belt dislocated
from its proper position?
Repair the installa-
tion condition of
timing belt. <Ref. to
ME(STI)-51, Tim-
ing Belt.>
Go to step 11.
11 CHECK FUEL LEVEL. Is the fuel meter indication
higher than the “Lower” level?
Go to step 12. Refill the fuel so
that the fuel meter
indication is higher
than the “Lower”
level, and proceed
to the next step. Go
to step 12.
12 CHECK STATUS OF MALFUNCTION INDI-
CATOR LIGHT.
1) Clear the memory using the Subaru Select
Monitor or general scan tool. <Ref. to
EN(STI)(diag)-59, Clear Memory Mode.>
2) Start the engine, and drive the vehicle 10
minutes or more.
Does the malfunction indicator
light illuminate or blink?
Go to step 14. Go to step 13.
13 CHECK CAUSE OF MISFIRE. Was the cause of misfire identi-
fied when the engine is run-
ning?
Finish diagnostics
operation, if the
engine has no
abnormality.
Repair the poor
contact of connec-
tor.
NOTE:
In this case, repair
the following item:
Poor contact of
ignition coil con-
nector
Poor contact of
fuel injector con-
nector on faulty
cylinders
Poor contact of
ECM connector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 181 ージ 20  
EN(STI)(diag)-182
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BL:DTC P0301 CYLINDER 1 MISFIRE DETECTED
NOTE:
For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(STI)(diag)-183, DTC P0304 CYLINDER 4
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
BM:DTC P0302 CYLINDER 2 MISFIRE DETECTED
NOTE:
For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(STI)(diag)-183, DTC P0304 CYLINDER 4
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
BN:DTC P0303 CYLINDER 3 MISFIRE DETECTED
NOTE:
For the diagnostic procedure, refer to DTC P0304. <Ref. to EN(STI)(diag)-183, DTC P0304 CYLINDER 4
MISFIRE DETECTED, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
14 CHECK AIR INTAKE SYSTEM. Is there any fault in air intake
system?
Repair the air
intake system.
NOTE:
Check the follow-
ing items.
Are there air
leaks or air suction
caused by loose or
dislocated nuts
and bolts?
Are there cracks
or any disconnec-
tion of hoses?
Go to step 15.
15 CHECK ALL CYLINDERS. Is there a fault in any cylinder? Repair or replace
the faulty part of
the faulty cylinder.
NOTE:
Check the follow-
ing items.
Spark plug
Fuel injector
Ignition coil
Compression ra-
tio
Skipping timing
belt teeth
Go to DTC P0171.
<Ref. to
EN(STI)(diag)-
158, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
Step Check Yes No
15WRX_STI_US_EN.book 182 ージ 20  
EN(STI)(diag)-183
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BO:DTC P0304 CYLINDER 4 MISFIRE DETECTED
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
Immediately at fault recognition (A misfire which could damage catalyst occurs.)
GENERAL DESCRIPTION <Ref. to GD(STI)-94, DTC P0304 CYLINDER 4 MISFIRE DETECTED, Diag-
nostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
Rough driving
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 183 ージ 20  
EN(STI)(diag)-184
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK OUTPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground on faulty cylinders.
Connector & terminal
#1 (B134) No. 10 (+) — Chassis ground (–):
#2 (B134) No. 11 (+) — Chassis ground (–):
#3 (B134) No. 12 (+) — Chassis ground (–):
#4 (B134) No. 13 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 6. Go to step 2.
10
B220
11
B550
216
51
52
53
54
E2
B21
48
2
1
E5
B134
10
11
12
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B134
8
5
6
10 11 12 13 14 15
72134
16
30
19 20 22
28 29
9
17
18 2521 23 24
3231
26 27
33 34
EN-10855
2
1
E16
2
1
E6
2
1
E17
13
E5
E6
E16
E17
21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
FUEL INJECTOR No. 4
FUEL INJECTOR No. 3
FUEL INJECTOR No. 2
FUEL INJECTOR No. 1
BATTERY
FUSE HOLDER
MAIN RELAY
15WRX_STI_US_EN.book 184 ージ 20  
EN(STI)(diag)-185
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector
on faulty cylinders.
3) Measure the resistance between fuel injec-
tor connector and engine ground on faulty cylin-
ders.
Connector & terminal
#1 (E5) No. 2 — Engine ground:
#2 (E16) No. 2 — Engine ground:
#3 (E6) No. 2 — Engine ground:
#4 (E17) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and fuel injector
connector.
3 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
Measure the resistance of harness between
ECM connector and fuel injector connector on
faulty cylinders.
Connector & terminal
#1 (B134) No. 10 — (E5) No. 2:
#2 (B134) No. 11 — (E16) No. 2:
#3 (B134) No. 12 — (E6) No. 2:
#4 (B134) No. 13 — (E17) No. 2:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and fuel injector
connector
Poor contact of
coupling connector
4 CHECK FUEL INJECTOR.
Measure the resistance between fuel injector
terminals on faulty cylinder.
Terminals
No. 1 — No. 2:
Is the resistance 5 — 20 Ω? Go to step 5. Replace the faulty
fuel injector. <Ref.
to FU(STI)-43,
Fuel Injector.>
5 CHECK POWER SUPPLY LINE.
1) Turn the ignition switch to ON.
2) Measure the voltage between fuel injector
connector of faulty cylinders and engine
ground.
Connector & terminal
#1 (E5) No. 1 (+) — Engine ground (–):
#2 (E16) No. 1 (+) — Engine ground (–):
#3 (E6) No. 1 (+) — Engine ground (–):
#4 (E17) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Repair the poor
contact of all con-
nectors in fuel
injector circuit.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
the main relay con-
nector and fuel in-
jector connector on
faulty cylinders
Poor contact of
coupling connector
Poor contact of
main relay connec-
tor
6 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector
on faulty cylinders.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground on faulty cylinders.
Connector & terminal
#1 (B134) No. 10 (+) — Chassis ground (–):
#2 (B134) No. 11 (+) — Chassis ground (–):
#3 (B134) No. 12 (+) — Chassis ground (–):
#4 (B134) No. 13 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and fuel injector
connectors.
Go to step 7.
Step Check Yes No
15WRX_STI_US_EN.book 185 ージ 20  
EN(STI)(diag)-186
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
7 CHECK FUEL INJECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between fuel injec-
tor terminals on faulty cylinder.
Terminals
No. 1 — No. 2:
Is the resistance 5 — 20 Ω? Go to step 8. Replace the faulty
fuel injector. <Ref.
to FU(STI)-43,
Fuel Injector.>
8 CHECK INSTALLATION OF CAMSHAFT PO-
SITION SENSOR/CRANKSHAFT POSITION
SENSOR.
Is the camshaft position sensor
or crankshaft position sensor
loosely installed?
Tighten the cam-
shaft position sen-
sor or crankshaft
position sensor.
<Ref. to FU(STI)-
35, Camshaft Posi-
tion Sensor.> <Ref.
to FU(STI)-34,
Crankshaft Posi-
tion Sensor.>
Go to step 9.
9 CHECK CRANK SPROCKET.
Remove the timing belt cover.
Is the crank sprocket rusted or
does it have broken teeth?
Replace the crank
sprocket. <Ref. to
ME(STI)-61, Crank
Sprocket.>
Go to step 10.
10 CHECK INSTALLATION CONDITION OF
TIMING BELT.
Turn the crankshaft, and align alignment mark
on crank sprocket with alignment mark on cylin-
der block.
ST 499987500 CRANKSHAFT
SOCKET
Is the timing belt dislocated
from its proper position?
Repair the installa-
tion condition of
timing belt. <Ref. to
ME(STI)-51, Tim-
ing Belt.>
Go to step 11.
11 CHECK FUEL LEVEL. Is the fuel meter indication
higher than the “Lower” level?
Go to step 12. Refill the fuel so
that the fuel meter
indication is higher
than the “Lower”
level, and proceed
to the next step. Go
to step 12.
12 CHECK STATUS OF MALFUNCTION INDI-
CATOR LIGHT.
1) Clear the memory using the Subaru Select
Monitor or general scan tool. <Ref. to
EN(STI)(diag)-59, Clear Memory Mode.>
2) Start the engine, and drive the vehicle 10
minutes or more.
Does the malfunction indicator
light illuminate or blink?
Go to step 14. Go to step 13.
13 CHECK CAUSE OF MISFIRE. Was the cause of misfire identi-
fied when the engine is run-
ning?
Finish diagnostics
operation, if the
engine has no
abnormality.
Repair the poor
contact of connec-
tor.
NOTE:
In this case, repair
the following item:
Poor contact of
ignition coil con-
nector
Poor contact of
fuel injector con-
nector on faulty
cylinders
Poor contact of
ECM connector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 186 ージ 20  
EN(STI)(diag)-187
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
14 CHECK AIR INTAKE SYSTEM. Is there any fault in air intake
system?
Repair the air
intake system.
NOTE:
Check the follow-
ing items.
Are there air
leaks or air suction
caused by loose or
dislocated nuts
and bolts?
Are there cracks
or any disconnec-
tion of hoses?
Go to step 15.
15 CHECK MISFIRE SYMPTOM.
1) Turn the ignition switch to ON.
2) Check for DTC. <Ref. to EN(STI)(diag)-42,
Read Diagnostic Trouble Code (DTC).>
Does the Subaru Select Moni-
tor or general scan tool indicate
only one DTC?
Go to step 18. Go to step 16.
16 CHECK DTC. Is DTC P0301 and P0303 dis-
played on the Subaru Select
Monitor or general scan tool?
Go to step 19. Go to step 17.
17 CHECK DTC. Is DTC P0302 and P0304 dis-
played on the Subaru Select
Monitor or general scan tool?
Go to step 20. Go to step 21.
18 ONLY ONE CYLINDER. Is there any fault in the cylin-
der?
Repair or replace
faulty parts.
NOTE:
Check the follow-
ing items.
Spark plug
Ignition coil
Fuel injector
Compression ra-
tio
Go to DTC P0171.
<Ref. to
EN(STI)(diag)-
158, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
19 GROUP OF #1 AND #3 CYLINDERS. Are there any faults in #1 and
#3 cylinders?
Repair or replace
faulty parts.
NOTE:
Check the follow-
ing items.
Spark plug
Ignition coil
Fuel injector
Compression ra-
tio
Skipping timing
belt teeth
Go to DTC P0171.
<Ref. to
EN(STI)(diag)-
158, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
20 GROUP OF #2 AND #4 CYLINDERS. Are there any faults in #2 and
#4 cylinders?
Repair or replace
faulty parts.
NOTE:
Check the follow-
ing items.
Spark plug
Ignition coil
Fuel injector
Compression ra-
tio
Skipping timing
belt teeth
Go to DTC P0171.
<Ref. to
EN(STI)(diag)-
158, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
Step Check Yes No
15WRX_STI_US_EN.book 187 ージ 20  
EN(STI)(diag)-188
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
21 CYLINDER AT RANDOM. Is the engine idle rough? Go to DTC P0171.
<Ref. to
EN(STI)(diag)-
158, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
Repair or replace
faulty parts.
NOTE:
Check the follow-
ing items.
Spark plug
Ignition coil
Fuel injector
Compression ra-
tio
Step Check Yes No
15WRX_STI_US_EN.book 188 ージ 20  
EN(STI)(diag)-189
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BP:DTC P0327 KNOCK SENSOR 1 CIRCUIT LOW (BANK 1 OR SINGLE SEN-
SOR)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-95, DTC P0327 KNOCK SENSOR 1 CIRCUIT LOW (BANK
1 OR SINGLE SENSOR), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Poor driving performance
Knocking occurs
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
KNOCK SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B137) No. 2 — (B134) No. 29:
Is the resistance less than 500
kΩ?
Go to step 2. Go to step 3.
B134A:
B137D:
E2B21
4
6
E14
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
1
2
A29
D2
EN-10864
D8
12
E14
ECM
KNOCK SENSOR
15WRX_STI_US_EN.book 189 ージ 20  
EN(STI)(diag)-190
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK KNOCK SENSOR.
1) Disconnect the connector from the knock
sensor.
2) Measure the resistance between knock
sensor connectors.
Terminals
No. 1 — No. 2:
Is the resistance less than 500
kΩ?
Replace the knock
sensor. <Ref. to
FU(STI)-38, Knock
Sensor.>
Repair the short
circuit to ground in
harness between
ECM connector
and knock sensor
connector.
NOTE:
The harness be-
tween both con-
nectors are
shielded. Remove
the shield and re-
pair the short cir-
cuit of harness.
3 CHECK INPUT SIGNAL OF ECM.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 2 (+) — Chassis ground (–):
Is the voltage 2 V or more? Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
Repair the short
circuit to ground in
harness between
ECM connector
and knock sensor
connector.
NOTE:
The harness be-
tween both con-
nectors are
shielded. Remove
the shield and re-
pair the short cir-
cuit of harness.
Step Check Yes No
15WRX_STI_US_EN.book 190 ージ 20  
EN(STI)(diag)-191
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BQ:DTC P0328 KNOCK SENSOR 1 CIRCUIT HIGH (BANK 1 OR SINGLE SEN-
SOR)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-96, DTC P0328 KNOCK SENSOR 1 CIRCUIT HIGH (BANK
1 OR SINGLE SENSOR), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Poor driving performance
Knocking occurs
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
KNOCK SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B137) No. 2 — (B134) No. 29:
Is the resistance 600 kΩ or
more?
Go to step 2. Repair the poor
contact of ECM
connector.
B134A:
B137D:
E2B21
4
6
E14
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
1
2
A29
D2
EN-10864
D8
12
E14
ECM
KNOCK SENSOR
15WRX_STI_US_EN.book 191 ージ 20  
EN(STI)(diag)-192
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK KNOCK SENSOR.
1) Disconnect the connector from the knock
sensor.
2) Measure the resistance between knock
sensor terminals.
Terminals
No. 1 — No. 2:
Is the resistance 600 kΩ or
more?
Replace the knock
sensor. <Ref. to
FU(STI)-38, Knock
Sensor.>
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and knock sensor
connector
Poor contact of
knock sensor con-
nector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 192 ージ 20  
EN(STI)(diag)-193
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BR:DTC P0335 CRANKSHAFT POSITION SENSOR “A” CIRCUIT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-97, DTC P0335 CRANKSHAFT POSITION SENSOR “A”
CIRCUIT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK CONDITION OF CRANKSHAFT PO-
SITION SENSOR.
Is the crankshaft position sen-
sor installation bolt tightened
securely?
Go to step 2. Tighten the crank-
shaft position sen-
sor installation bolt
securely. <Ref. to
FU(STI)-34,
Crankshaft Posi-
tion Sensor.>
21
E10
B137
E2B21
14
3
E10
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
1
2
17
25
EN-09557
31
ECM
CRANKSHAFT
POSITION SENSOR
15WRX_STI_US_EN.book 193 ージ 20  
EN(STI)(diag)-194
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK CRANKSHAFT POSITION SENSOR.
1) Turn the ignition switch to OFF.
2) Remove the crankshaft position sensor.
3) Measure the resistance between terminals
of crankshaft position sensor.
Terminals
No. 1 — No. 2:
Is the resistance between 1 and
4 kΩ?
Go to step 3. Replace the crank-
shaft position sen-
sor. <Ref. to
FU(STI)-34,
Crankshaft Posi-
tion Sensor.>
3 CHECK HARNESS BETWEEN ECM AND
CRANKSHAFT POSITION SENSOR CON-
NECTOR.
1) Disconnect the connector from ECM.
2) Measure the resistance of harness between
ECM connector and crankshaft position sensor
connector.
Connector & terminal
(B137) No. 17 — (E10) No. 1:
(B137) No. 25 — (E10) No. 2:
Is the resistance less than 1 Ω? Repair the poor
contact of ECM
and crankshaft
position sensor
connector.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and crankshaft po-
sition sensor con-
nector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 194 ージ 20  
EN(STI)(diag)-195
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BS:DTC P0336 CRANKSHAFT POSITION SENSOR “A” CIRCUIT RANGE/PER-
FORMANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-99, DTC P0336 CRANKSHAFT POSITION SENSOR “A”
CIRCUIT RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK CONDITION OF CRANKSHAFT PO-
SITION SENSOR.
Turn the ignition switch to OFF.
Is the crankshaft position sen-
sor installation bolt tightened
securely?
Go to step 2. Tighten the crank-
shaft position sen-
sor installation bolt
securely. <Ref. to
FU(STI)-34,
Crankshaft Posi-
tion Sensor.>
2 CHECK CRANK SPROCKET.
Remove the timing belt cover.
Are crank sprocket teeth
cracked or damaged?
Replace the crank
sprocket. <Ref. to
ME(STI)-61, Crank
Sprocket.>
Go to step 3.
3 CHECK INSTALLATION CONDITION OF
TIMING BELT.
Turn the crankshaft, and align alignment mark
on crank sprocket with alignment mark on cylin-
der block.
ST 499987500 CRANKSHAFT
SOCKET
Is the timing belt dislocated
from its proper position?
Repair the installa-
tion condition of
timing belt. <Ref. to
ME(STI)-51, Tim-
ing Belt.>
Replace the crank-
shaft position sen-
sor. <Ref. to
FU(STI)-34,
Crankshaft Posi-
tion Sensor.>
15WRX_STI_US_EN.book 195 ージ 20  
EN(STI)(diag)-196
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BT:DTC P0340 CAMSHAFT POSITION SENSOR “A” CIRCUIT (BANK 1 OR SIN-
GLE SENSOR)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-101, DTC P0340 CAMSHAFT POSITION SENSOR “A” CIR-
CUIT (BANK 1 OR SINGLE SENSOR), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
2
1
3
E36E35
EN-10865
B550
21611
B220
10
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
19
18
20 21
22
23
26
24
25
27
28 29
30 31
98
15
1413121110
17
16
1234567
B137
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
1
13
2
5
48
E2
B21
2
3
B137
24
30
E35
1
2
3
16
E36
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
INTAKE CAMSHAFT
POSITION SENSOR RH
INTAKE CAMSHAFT
POSITION SENSOR LH
MAIN RELAY
BATTERY
FUSE HOLDER
15WRX_STI_US_EN.book 196 ージ 20  
EN(STI)(diag)-197
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK POWER SUPPLY OF CAMSHAFT
POSITION SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from camshaft
position sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between camshaft
position sensor connector and engine ground.
Connector & terminal
(E36) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit or
short circuit to
ground in harness
between main re-
lay connector and
camshaft position
sensor connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and camshaft position sensor connector.
Connector & terminal
(B137) No. 24 — (E36) No. 2:
(B137) No. 30 — (E36) No. 3:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and camshaft posi-
tion sensor con-
nector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
Measure the resistance between camshaft
position sensor connector and engine ground.
Connector & terminal
(E36) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 4. Repair short cir-
cuit to ground in
harness between
ECM connector
and camshaft posi-
tion sensor con-
nector.
4 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
Measure the voltage between camshaft posi-
tion sensor connector and engine ground.
Connector & terminal
(E36) No. 2 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and cam-
shaft position
sensor connector.
Go to step 5.
5 CHECK CONDITION OF CAMSHAFT POSI-
TION SENSOR.
Is the camshaft position sensor
installation bolt tightened
securely?
Go to step 6. Tighten the cam-
shaft position sen-
sor installation bolt
securely. <Ref. to
FU(STI)-35, Cam-
shaft Position Sen-
sor.>
6 CHECK CAMSHAFT POSITION SENSOR.
Check the waveform of the camshaft position
sensor. <Ref. to EN(STI)(diag)-19, Engine Con-
trol Module (ECM) I/O Signal.>
Is there any abnormality in
waveform?
Replace the cam-
shaft position sen-
sor. <Ref. to
FU(STI)-35, Cam-
shaft Position Sen-
sor.>
Repair the follow-
ing item.
Poor contact of
ECM connector
Poor contact of
camshaft position
sensor connector
Poor contact of
coupling connector
15WRX_STI_US_EN.book 197 ージ 20  
EN(STI)(diag)-198
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BU:DTC P0341 CAMSHAFT POSITION SENSOR "A" CIRCUIT RANGE/PERFOR-
MANCE (BANK 1 OR SINGLE SENSOR)
NOTE:
For the diagnostic procedure, refer to DTC P0340. <Ref. to EN(STI)(diag)-196, DTC P0340 CAMSHAFT PO-
SITION SENSOR “A” CIRCUIT (BANK 1 OR SINGLE SENSOR), Diagnostic Procedure with Diagnostic
Trouble Code (DTC).>
15WRX_STI_US_EN.book 198 ージ 20  
EN(STI)(diag)-199
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BV:DTC P0345 CAMSHAFT POSITION SENSOR “A” CIRCUIT (BANK 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-104, DTC P0345 CAMSHAFT POSITION SENSOR “A” CIR-
CUIT (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
2
1
3
E36E35
EN-10865
B550
21611
B220
10
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
19
18
20 21
22
23
26
24
25
27
28 29
30 31
98
15
1413121110
17
16
1234567
B137
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
1
13
2
5
48
E2
B21
2
3
B137
24
30
E35
1
2
3
16
E36
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
INTAKE CAMSHAFT
POSITION SENSOR RH
INTAKE CAMSHAFT
POSITION SENSOR LH
MAIN RELAY
BATTERY
FUSE HOLDER
15WRX_STI_US_EN.book 199 ージ 20  
EN(STI)(diag)-200
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK POWER SUPPLY OF CAMSHAFT
POSITION SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from camshaft
position sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between camshaft
position sensor connector and engine ground.
Connector & terminal
(E35) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit or
short circuit to
ground in harness
between main re-
lay connector and
camshaft position
sensor connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and camshaft position sensor connector.
Connector & terminal
(B137) No. 16 — (E35) No. 2:
(B137) No. 30 — (E35) No. 3:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and camshaft posi-
tion sensor con-
nector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
Measure the resistance between camshaft
position sensor connector and engine ground.
Connector & terminal
(E35) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 4. Repair short cir-
cuit to ground in
harness between
ECM connector
and camshaft posi-
tion sensor con-
nector.
4 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
Measure the voltage between camshaft posi-
tion sensor connector and engine ground.
Connector & terminal
(E35) No. 2 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and cam-
shaft position
sensor connector.
Go to step 5.
5 CHECK CONDITION OF CAMSHAFT POSI-
TION SENSOR.
Is the camshaft position sensor
installation bolt tightened
securely?
Go to step 6. Tighten the cam-
shaft position sen-
sor installation bolt
securely. <Ref. to
FU(STI)-35, Cam-
shaft Position Sen-
sor.>
6 CHECK CAMSHAFT POSITION SENSOR.
Check the waveform of the camshaft position
sensor. <Ref. to EN(STI)(diag)-19, Engine Con-
trol Module (ECM) I/O Signal.>
Is there any abnormality in
waveform?
Replace the cam-
shaft position sen-
sor. <Ref. to
FU(STI)-35, Cam-
shaft Position Sen-
sor.>
Repair the follow-
ing item.
Poor contact of
ECM connector
Poor contact of
camshaft position
sensor connector
Poor contact of
coupling connector
15WRX_STI_US_EN.book 200 ージ 20  
EN(STI)(diag)-201
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BW:DTC P0346 CAMSHAFT POSITION SENSOR "A" CIRCUIT RANGE/PER-
FORMANCE (BANK 2)
NOTE:
For the diagnostic procedure, refer to DTC P0345. <Ref. to EN(STI)(diag)-199, DTC P0345 CAMSHAFT PO-
SITION SENSOR “A” CIRCUIT (BANK 2), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
15WRX_STI_US_EN.book 201 ージ 20  
EN(STI)(diag)-202
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BX:DTC P0351 IGNITION COIL A PRIMARY/SECONDARY CIRCUIT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-105, DTC P0351 IGNITION COIL A PRIMARY/SECOND-
ARY CIRCUIT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
WP
OP
B72
7856
3412
E32E31
E34E33
123
WP
OP
WP
OP
B72
B550
1024
14
B225
36 37
10
31
20
9
E2B21
49
2
1
3
E31
B134
21
22
31
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B134
8
5
6
10 11 12 13 14 15
72134
16
30
19 20 22
28 29
9
17
18 2521 23 24
3231
26 27
33 34
EN-10854
2
1
3
E32
2
1
3
E33
2
1
3
E34
32
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-6
ECM
BATTERY
IGNITION COIL No. 4
IGNITION COIL No. 3
IGNITION COIL No. 2
IGNITION COIL No. 1
IG RELAY 1
(PUSH BUTTON
START)
FUSE
HOLDER
F/B No. 12
IGNITION SWITCH
MAIN SBF
: WITHOUT PUSH BUTTON START
: WITH PUSH BUTTON START
15WRX_STI_US_EN.book 202 ージ 20  
EN(STI)(diag)-203
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK IGNITION COIL POWER SUPPLY
CIRCUIT.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ignition coil.
3) Turn the ignition switch to ON.
4) Measure the voltage between ignition coil
connector and engine ground.
Connector & terminal
DTC P0351; (E31) No. 3 (+) — Engine
ground (–):
DTC P0352; (E32) No. 3 (+) — Engine
ground (–):
DTC P0353; (E33) No. 3 (+) — Engine
ground (–):
DTC P0354; (E34) No. 3 (+) — Engine
ground (–):
Is the voltage 10 V or more? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit or
short circuit to
ground in harness
of power supply
circuit
Blown out of fuse
Poor contact of
coupling connector
2 CHECK HARNESS OF IGNITION COIL
GROUND CIRCUIT.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness between
ignition coil connector and engine ground.
Connector & terminal
DTC P0351; (E31) No. 2 — Engine ground:
DTC P0352; (E32) No. 2 — Engine ground:
DTC P0353; (E33) No. 2 — Engine ground:
DTC P0354; (E34) No. 2 — Engine ground:
Is the resistance less than 5 Ω? Go to step 3. Repair the open
circuit in harness
between ignition
coil connector and
engine grounding
terminal.
3 CHECK HARNESS BETWEEN ECM AND IG-
NITION COIL CONNECTOR.
1) Disconnect the connector from ECM.
2) Measure the resistance between ignition
coil connector and engine ground.
Connector & terminal
DTC P0351; (E31) No. 1 — Engine ground:
DTC P0352; (E32) No. 1 — Engine ground:
DTC P0353; (E33) No. 1 — Engine ground:
DTC P0354; (E34) No. 1 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 4. Repair the ground
short circuit of har-
ness between
ECM connector
and ignition coil
connector.
4 CHECK HARNESS BETWEEN ECM AND IG-
NITION COIL CONNECTOR.
Measure the resistance of harness between
ECM connector and ignition coil connector.
Connector & terminal
DTC P0351; (B134) No. 21 — (E31) No. 1:
DTC P0352; (B134) No. 22 — (E32) No. 1:
DTC P0353; (B134) No. 31 — (E33) No. 1:
DTC P0354; (B134) No. 32 — (E34) No. 1:
Is the resistance less than 1 Ω? Go to step 5. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and the ignition coil
connector
Poor contact of
coupling connector
5 CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.
Is there poor contact of ECM
connector?
Repair the poor
contact of ECM
connector.
Go to step
6.
6 CHECK SPARK PLUG CONDITION.
1) Remove the spark plug of the correspond-
ing cylinder. <Ref. to IG(STI)-4, REMOVAL,
Spark Plug.>
2) Check the spark plug condition. <Ref. to
IG(STI)-5, INSPECTION, Spark Plug.>
Is the spark plug condition nor-
mal?
Replace the igni-
tion coil. <Ref. to
IG(STI)-7, Ignition
Coil.>
Replace the spark
plug. <Ref. to
IG(STI)-4, Spark
Plug.>
15WRX_STI_US_EN.book 203 ージ 20  
EN(STI)(diag)-204
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
BY:DTC P0352 IGNITION COIL B PRIMARY/SECONDARY CIRCUIT
NOTE:
For the diagnostic procedure, refer to DTC P0351. <Ref. to EN(STI)(diag)-202, DTC P0351 IGNITION COIL
A PRIMARY/SECONDARY CIRCUIT, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
BZ:DTC P0353 IGNITION COIL C PRIMARY/SECONDARY CIRCUIT
NOTE:
For the diagnostic procedure, refer to DTC P0351. <Ref. to EN(STI)(diag)-202, DTC P0351 IGNITION COIL
A PRIMARY/SECONDARY CIRCUIT, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
CA:DTC P0354 IGNITION COIL D PRIMARY/SECONDARY CIRCUIT
NOTE:
For the diagnostic procedure, refer to DTC P0351. <Ref. to EN(STI)(diag)-202, DTC P0351 IGNITION COIL
A PRIMARY/SECONDARY CIRCUIT, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
15WRX_STI_US_EN.book 204 ージ 20  
EN(STI)(diag)-205
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CB:DTC P0365 CAMSHAFT POSITION SENSOR “B” CIRCUIT (BANK 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-106, DTC P0365 CAMSHAFT POSITION SENSOR “B” CIR-
CUIT (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
EN-10866
B550
216
10
B220
11
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
19
18
20 21
22
23
26
24
25
27
28 29
30 31
98
15
1413121110
17
16
1234567
B137
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
1
26
15
5
48
E2
B21
2
3
B137
23
30
E65
1
2
3
29
E62
2
1
3
E65E62
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
EXHAUST CAMSHAFT
POSITION SENSOR RH
EXHAUST CAMSHAFT
POSITION SENSOR LH
MAIN RELAY
BATTERY
FUSE HOLDER
15WRX_STI_US_EN.book 205 ージ 20  
EN(STI)(diag)-206
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK POWER SUPPLY OF CAMSHAFT
POSITION SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from camshaft
position sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between camshaft
position sensor connector and engine ground.
Connector & terminal
(E62) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit or
short circuit to
ground in harness
between main re-
lay connector and
camshaft position
sensor connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and camshaft position sensor connector.
Connector & terminal
(B137) No. 23 — (E62) No. 2:
(B137) No. 30 — (E62) No. 3:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and camshaft posi-
tion sensor con-
nector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
Measure the resistance between camshaft
position sensor connector and engine ground.
Connector & terminal
(E62) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 4. Repair short cir-
cuit to ground in
harness between
ECM connector
and camshaft posi-
tion sensor con-
nector.
4 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
Measure the voltage between camshaft posi-
tion sensor connector and engine ground.
Connector & terminal
(E62) No. 2 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and cam-
shaft position
sensor connector.
Go to step 5.
5 CHECK CONDITION OF CAMSHAFT POSI-
TION SENSOR.
Is the camshaft position sensor
installation bolt tightened
securely?
Go to step 6. Tighten the cam-
shaft position sen-
sor installation bolt
securely. <Ref. to
FU(STI)-35, Cam-
shaft Position Sen-
sor.>
6 CHECK CAMSHAFT POSITION SENSOR.
Check the waveform of the camshaft position
sensor. <Ref. to EN(STI)(diag)-19, Engine Con-
trol Module (ECM) I/O Signal.>
Is there any abnormality in
waveform?
Replace the cam-
shaft position sen-
sor. <Ref. to
FU(STI)-35, Cam-
shaft Position Sen-
sor.>
Repair the follow-
ing item.
Poor contact of
ECM connector
Poor contact of
camshaft position
sensor connector
Poor contact of
coupling connector
15WRX_STI_US_EN.book 206 ージ 20  
EN(STI)(diag)-207
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CC:DTC P0366 CAMSHAFT POSITION SENSOR B CIRCUIT RANGE/PERFOR-
MANCE (BANK 1)
NOTE:
For the diagnostic procedure, refer to DTC P0365. <Ref. to EN(STI)(diag)-205, DTC P0365 CAMSHAFT PO-
SITION SENSOR “B” CIRCUIT (BANK 1), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
15WRX_STI_US_EN.book 207 ージ 20  
EN(STI)(diag)-208
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CD:DTC P0390 CAMSHAFT POSITION SENSOR “B” CIRCUIT (BANK 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-107, DTC P0390 CAMSHAFT POSITION SENSOR “B” CIR-
CUIT (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
EN-10866
B550
216
10
B220
11
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
19
18
20 21
22
23
26
24
25
27
28 29
30 31
98
15
1413121110
17
16
1234567
B137
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
1
26
15
5
48
E2
B21
2
3
B137
23
30
E65
1
2
3
29
E62
2
1
3
E65E62
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
EXHAUST CAMSHAFT
POSITION SENSOR RH
EXHAUST CAMSHAFT
POSITION SENSOR LH
MAIN RELAY
BATTERY
FUSE HOLDER
15WRX_STI_US_EN.book 208 ージ 20  
EN(STI)(diag)-209
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK POWER SUPPLY OF CAMSHAFT
POSITION SENSOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from camshaft
position sensor.
3) Turn the ignition switch to ON.
4) Measure the voltage between camshaft
position sensor connector and engine ground.
Connector & terminal
(E65) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit or
short circuit to
ground in harness
between main re-
lay connector and
camshaft position
sensor connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and camshaft position sensor connector.
Connector & terminal
(B137) No. 29 — (E65) No. 2:
(B137) No. 30 — (E65) No. 3:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and camshaft posi-
tion sensor con-
nector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
Measure the resistance between camshaft
position sensor connector and engine ground.
Connector & terminal
(E65) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 4. Repair short cir-
cuit to ground in
harness between
ECM connector
and camshaft posi-
tion sensor con-
nector.
4 CHECK HARNESS BETWEEN ECM AND
CAMSHAFT POSITION SENSOR CONNEC-
TOR.
Measure the voltage between camshaft posi-
tion sensor connector and engine ground.
Connector & terminal
(E65) No. 2 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and cam-
shaft position
sensor connector.
Go to step 5.
5 CHECK CONDITION OF CAMSHAFT POSI-
TION SENSOR.
Is the camshaft position sensor
installation bolt tightened
securely?
Go to step 6. Tighten the cam-
shaft position sen-
sor installation bolt
securely. <Ref. to
FU(STI)-35, Cam-
shaft Position Sen-
sor.>
6 CHECK CAMSHAFT POSITION SENSOR.
Check the waveform of the camshaft position
sensor. <Ref. to EN(STI)(diag)-19, Engine Con-
trol Module (ECM) I/O Signal.>
Is there any abnormality in
waveform?
Replace the cam-
shaft position sen-
sor. <Ref. to
FU(STI)-35, Cam-
shaft Position Sen-
sor.>
Repair the follow-
ing item.
Poor contact of
ECM connector
Poor contact of
camshaft position
sensor connector
Poor contact of
coupling connector
15WRX_STI_US_EN.book 209 ージ 20  
EN(STI)(diag)-210
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CE:DTC P0391 CAMSHAFT POSITION SENSOR B CIRCUIT RANGE/PERFOR-
MANCE (BANK 2)
NOTE:
For the diagnostic procedure, refer to DTC P0390. <Ref. to EN(STI)(diag)-208, DTC P0390 CAMSHAFT PO-
SITION SENSOR “B” CIRCUIT (BANK 2), Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
15WRX_STI_US_EN.book 210 ージ 20  
EN(STI)(diag)-211
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CF:DTC P0410 SECONDARY AIR INJECTION SYSTEM
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-108, DTC P0410 SECONDARY AIR INJECTION SYSTEM,
Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 211 ージ 20  
EN(STI)(diag)-212
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK SECONDARY AIR PUMP FUSE.
Check if the secondary air pump fuse (60 A) is
blown out.
Is the fuse blown out? Go to step 2. Go to step 3.
ECM
A:
M/B
F37
B: B143
E40
B143B:
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
F37A:
1234
56789
10 11 12 13 14 15 16 17 18 19 20
12
F11
5
11
15
1
2
9
10
34 7
12 13
8
6
16
14
F9
12
E41
123
456
E40
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
F9
A13
28
1
6
47
E2
B21
46
B550
216
B220
11
10
1
2
3
6
4
1
2
2
60A
10A
14
12
11
13
15
16
6
5
7
10
8
9
4
1
3
2
B10
B20
A5B2
A17B13
A20
A18B12
B4 A8
A19
D9
A29
B27
B20
B8
B137D:
B135B:
B134A:
A16
B14
1
E41 F11
EN-10867
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SECONDARY
AIR PUMP
SECONDARY
AIR COMBINATION
VALVE RH
SECONDARY
AIR PUMP RELAY
SECONDARY
AIR COMBINATION
VALVE RELAY 2
SECONDARY
AIR COMBINATION
VALVE RELAY 1
MAIN SBF
MAIN RELAY
BATTERY
FUSE HOLDER
RELAY HOLDER
SECONDARY AIR
COMBINATION VALVE LH
(WITH BUILT-IN
PRESSURE SENSOR)
15WRX_STI_US_EN.book 212 ージ 20  
EN(STI)(diag)-213
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK HARNESS BETWEEN FUSE BOX
AND SECONDARY AIR PUMP CONNECTOR.
1) Remove the secondary air pump fuse from
the fuse box.
2) Disconnect the secondary air pump con-
nector.
3) Measure the resistance between the sec-
ondary air pump fuse and secondary air pump
connector, and chassis ground.
Connector & terminal
(F9) No. 16 — Chassis ground:
(F11) No. 2 — Chassis ground:
Is the resistance 1 MΩ or
more?
Replace the fuse
with a new part,
and connect the
secondary air
pump connector.
Go to step 3.
Repair ground
short of the har-
ness between the
fuse box and the
secondary air
pump connector.
3 CHECK SECONDARY AIR PUMP OPERA-
TION.
CAUTION:
Try your best to complete the confirmation
process of this inspection in one try. This in-
spection will put a heavy workload on the
secondary air pump, so the continuous op-
eration may cause damage to the pump. Do
not operate the pump continuously for more
than three times. If you need to operate the
pump further, turn the ignition switch to
OFF and wait for at least two hours.
1) Install the delivery mode fuse.
2) Turn the ignition switch to ON.
3) Perform operation check for the secondary
air pump using the Subaru Select Monitor.
NOTE:
The compulsory operation using the Subaru
Select Monitor is performed only for 10 seconds
in order to protect the secondary air pump.
When you want to operate the pump again, dis-
connect the ground cable from battery, wait at
least one minute, and perform the clear memo-
ry operation of ECM. Then, perform the forced
operation using the Subaru Select Monitor.
For detailed procedures, refer to “System Op-
eration Check Mode”. <Ref. to EN(STI)(diag)-
60, System Operation Check Mode.>
Does the secondary air pump
operate?
Go to step 4. Go to step 5.
4 CHECK DUCT BETWEEN SECONDARY AIR
PUMP AND COMBINATION VALVE.
Check the duct between secondary air pump
and combination valve.
Is there damage, clog or dis-
connection of the duct?
Replace, clean or
connect the duct.
Replace the sec-
ondary air combi-
nation valve LH.
<Ref. to EC(STI)-
54, Secondary Air
Combination
Valve.>
Step Check Yes No
15WRX_STI_US_EN.book 213 ージ 20  
EN(STI)(diag)-214
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
5 CHECK POWER SUPPLY TO SECONDARY
AIR PUMP.
1) Turn the ignition switch to OFF.
2) Disconnect the battery negative terminal,
wait for 1 minute, and connect it again.
3) Disconnect the secondary air pump con-
nector.
4) Install the delivery mode fuse.
5) Turn the ignition switch to ON.
6) Using the Subaru Select Monitor, measure
the voltage between the secondary air pump
connector and chassis ground while the sec-
ondary air pump is operating.
NOTE:
The compulsory operation using the Subaru
Select Monitor is performed only for 10 seconds
in order to protect the secondary air pump.
When you want to operate the pump again, dis-
connect the ground cable from battery, wait at
least one minute, and perform the clear memo-
ry operation of ECM. Then, perform the forced
operation using the Subaru Select Monitor.
For detailed procedures, refer to “System Op-
eration Check Mode”. <Ref. to EN(STI)(diag)-
60, System Operation Check Mode.>
Connector & terminal
(F11) No. 2 (+) — Chassis ground (–):
Is the voltage 10 V or more? Replace the sec-
ondary air pump.
<Ref. to EC(STI)-
53, Secondary Air
Pump.>
Go to step 6.
6 CHECK HARNESS BETWEEN SECONDARY
AIR PUMP RELAY AND SECONDARY AIR
PUMP CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the secondary air pump relay.
3) Measure the resistance of harness between
secondary air pump relay connector and sec-
ondary air pump connector.
Connector & terminal
(F9) No. 11 — (F11) No. 2:
Is the resistance less than 1 Ω? Go to step 7. Repair the open
circuit in harness
between second-
ary air pump relay
connector and sec-
ondary air pump
connector.
7 CHECK HARNESS BETWEEN SECONDARY
AIR PUMP CONNECTOR AND CHASSIS
GROUND.
Measure the resistance of the harness between
secondary air pump connector and chassis
ground.
Connector & terminal
(F11) No. 1 — Chassis ground:
Is the resistance less than 5 Ω? Go to step 8. Repair the open
circuit of the har-
ness between sec-
ondary air pump
connector and
chassis ground.
8 CHECK SECONDARY AIR PUMP RELAY.
1) Connect the battery to terminals No. 12 and
No. 13 of the secondary air pump relay.
2) Measure the resistance between secondary
air pump relay terminals.
Terminals
No. 14 — No. 11:
Is the resistance less than 1 Ω? Go to step 9. Replace the sec-
ondary air pump
relay. <Ref. to
EN(STI)(diag)-8,
Electrical Compo-
nent Location.>
Step Check Yes No
15WRX_STI_US_EN.book 214 ージ 20  
EN(STI)(diag)-215
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
9 CHECK SECONDARY AIR PUMP RELAY
POWER SUPPLY.
1) Turn the ignition switch to ON.
2) Measure the voltage between the second-
ary air pump relay connector and chassis
ground.
Connector & terminal
(F9) No. 14 (+) — Chassis ground (–):
(F9) No. 12 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 10. Repair the open or
ground short circuit
of power supply
circuit.
10 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR PUMP RELAY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the ECM connector.
3) Measure the resistance of harness between
ECM connector and secondary air pump relay
connector.
Connector & terminal
(B135) No. 27 — (F9) No. 13:
Is the resistance less than 1 Ω? Repair the poor
contact of ECM
connector.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and secondary air
pump relay con-
nector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 215 ージ 20  
EN(STI)(diag)-216
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CG:DTC P0411 SECONDARY AIR INJECTION SYSTEM INCORRECT FLOW DE-
TECTED
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-114, DTC P0411 SECONDARY AIR INJECTION SYSTEM
INCORRECT FLOW DETECTED, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK SECONDARY AIR COMBINATION
VALVE.
Check the pipe between the secondary air com-
bination valve and cylinder head.
Is there damage or disconnec-
tion of the pipe?
Replace the pipe
between second-
ary air combination
valve and cylinder
head. <Ref. to
EC(STI)-54, Sec-
ondary Air Combi-
nation Valve.>
Go to step 2.
2 CHECK SECONDARY AIR COMBINATION
VALVE.
Race the engine at 2,000 rpm to check whether
or not the exhaust leak is heard.
Is there any exhaust leak? Replace the pipe
between second-
ary air combination
valve and cylinder
head. <Ref. to
EC(STI)-54, Sec-
ondary Air Combi-
nation Valve.>
Repair the poor
contact of ECM
connector.
15WRX_STI_US_EN.book 216 ージ 20  
EN(STI)(diag)-217
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CH:DTC P0413 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE “A”
CIRCUIT OPEN
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-115, DTC P0413 SECONDARY AIR INJECTION SYSTEM
SWITCHING VALVE “A” CIRCUIT OPEN, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 217 ージ 20  
EN(STI)(diag)-218
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
A:
M/B
F37
B: B143
E40
B143B:
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
F37A:
1234
56789
10 11 12 13 14 15 16 17 18 19 20
12
F11
5
11
15
1
2
9
10
34 7
12 13
8
6
16
14
F9
12
E41
123
456
E40
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
F9
A13
28
1
6
47
E2
B21
46
B550
216
B220
11
10
1
2
3
6
4
1
2
2
60A
10A
14
12
11
13
15
16
6
5
7
10
8
9
4
1
3
2
B10
B20
A5B2
A17B13
A20
A18B12
B4 A8
A19
D9
A29
B27
B20
B8
B137D:
B135B:
B134A:
A16
B14
1
E41 F11
EN-10867
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SECONDARY
AIR PUMP
SECONDARY
AIR COMBINATION
VALVE RH
SECONDARY
AIR PUMP RELAY
SECONDARY
AIR COMBINATION
VALVE RELAY 2
SECONDARY
AIR COMBINATION
VALVE RELAY 1
MAIN SBF
MAIN RELAY
BATTERY
FUSE HOLDER
RELAY HOLDER
SECONDARY AIR
COMBINATION VALVE LH
(WITH BUILT-IN
PRESSURE SENSOR)
15WRX_STI_US_EN.book 218 ージ 20  
EN(STI)(diag)-219
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 1 CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Remove the secondary air combination
valve relay 1.
4) Measure the resistance of harness between
ECM connector and secondary air combination
valve relay 1 connector.
Connector & terminal
(B135) No. 8 — (F9) No. 2:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and secondary air
combination valve
relay 1 connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 1 CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B135) No. 8 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and secondary air
combination valve
relay 1 connector.
3 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 2 CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Remove the secondary air combination
valve relay 2.
4) Measure the resistance of harness between
ECM connector and secondary air combination
valve relay 2 connector.
Connector & terminal
(B135) No. 20 — (F9) No. 9:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and secondary air
combination valve
relay 2 connector
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 2 CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B135) No. 20 — Chassis ground:
Is the resistance 1 MΩ or
more?
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
Repair the short
circuit to ground in
harness between
ECM connector
and secondary air
combination valve
relay 2 connector.
15WRX_STI_US_EN.book 219 ージ 20  
EN(STI)(diag)-220
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CI: DTC P0414 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE “A”
CIRCUIT SHORTED
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-116, DTC P0414 SECONDARY AIR INJECTION SYSTEM
SWITCHING VALVE “A” CIRCUIT SHORTED, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 220 ージ 20  
EN(STI)(diag)-221
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
A:
M/B
F37
B: B143
E40
B143B:
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
F37A:
1234
56789
10 11 12 13 14 15 16 17 18 19 20
12
F11
5
11
15
1
2
9
10
34 7
12 13
8
6
16
14
F9
12
E41
123
456
E40
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
F9
A13
28
1
6
47
E2
B21
46
B550
216
B220
11
10
1
2
3
6
4
1
2
2
60A
10A
14
12
11
13
15
16
6
5
7
10
8
9
4
1
3
2
B10
B20
A5B2
A17B13
A20
A18B12
B4 A8
A19
D9
A29
B27
B20
B8
B137D:
B135B:
B134A:
A16
B14
1
E41 F11
EN-10867
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SECONDARY
AIR PUMP
SECONDARY
AIR COMBINATION
VALVE RH
SECONDARY
AIR PUMP RELAY
SECONDARY
AIR COMBINATION
VALVE RELAY 2
SECONDARY
AIR COMBINATION
VALVE RELAY 1
MAIN SBF
MAIN RELAY
BATTERY
FUSE HOLDER
RELAY HOLDER
SECONDARY AIR
COMBINATION VALVE LH
(WITH BUILT-IN
PRESSURE SENSOR)
15WRX_STI_US_EN.book 221 ージ 20  
EN(STI)(diag)-222
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CJ:DTC P0416 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE “B”
CIRCUIT OPEN
NOTE:
For the diagnostic procedure, refer to DTC P0413. <Ref. to EN(STI)(diag)-217, DTC P0413 SECONDARY
AIR INJECTION SYSTEM SWITCHING VALVE “A” CIRCUIT OPEN, Diagnostic Procedure with Diagnostic
Trouble Code (DTC).>
CK:DTC P0417 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE “B”
CIRCUIT SHORTED
NOTE:
For the diagnostic procedure, refer to DTC P0414. <Ref. to EN(STI)(diag)-220, DTC P0414 SECONDARY
AIR INJECTION SYSTEM SWITCHING VALVE “A” CIRCUIT SHORTED, Diagnostic Procedure with Diag-
nostic Trouble Code (DTC).>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 1 CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Remove the secondary air combination
valve relay 1.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B135) No. 8 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and secondary air
combination valve
relay 1 connector.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 2 CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Remove the secondary air combination
valve relay 2.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B135) No. 20 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and secondary air
combination valve
relay 2 connector.
Repair the poor
contact of ECM
connector.
15WRX_STI_US_EN.book 222 ージ 20  
EN(STI)(diag)-223
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CL:DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-117, DTC P0420 CATALYST SYSTEM EFFICIENCY BE-
LOW THRESHOLD (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Idle mixture is out of specifications.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 223 ージ 20  
EN(STI)(diag)-224
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK EXHAUST SYSTEM.
Check for gas leaks or air suction caused by
loose or dislocated nuts and bolts, and open
hole at exhaust pipes.
NOTE:
Check the following positions.
Between cylinder head and front exhaust
pipe
Between front exhaust pipe and front catalytic
converter
Between front catalytic converter and rear
catalytic converter
Loose or improperly attached front oxygen
(A/F) sensor or rear oxygen sensor
Is there any fault in exhaust
system?
Repair or replace
the exhaust sys-
tem. <Ref. to
EX(STI)-2, Gen-
eral Description.>
Go to step 2.
2 CHECK WAVEFORM DATA ON THE SUBA-
RU SELECT MONITOR (WHILE DRIVING).
1) Drive at a constant speed between 80 —
112 km/h (50 — 70 MPH).
2) After 5 minutes have elapsed in the condi-
tion of step 1), use the Subaru Select Monitor
while still driving to read the waveform data.
At normal condition
At abnormal condition (numerous inversion)
Is a normal waveform dis-
played?
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
Go to step 3.
EN-06666
1
0
1.5
0.5
10 sec/div
REAR OXYGEN
SENSOR VOLTAGE
(V)
A/F SENSOR
OUTPUT LAMBDA 1
EN-06667
1
0
1.5
0.5
10 sec/div
REAR OXYGEN
SENSOR VOLTAGE
(V)
A/F SENSOR
OUTPUT LAMBDA 1
15WRX_STI_US_EN.book 224 ージ 20  
EN(STI)(diag)-225
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
3 CHECK WAVEFORM DATA ON THE SUBA-
RU SELECT MONITOR (WHILE IDLING).
1) Run the engine at idle.
2) In the condition of step 1), use the Subaru
Select Monitor to read the waveform data.
At normal condition
At abnormal condition 1 (numerous inversion)
At abnormal condition 2 (noise input)
Is a normal waveform dis-
played?
Go to step 4. The waveform is
displayed at abnor-
mal condition 1: Go
to step 4.
The waveform is
displayed at abnor-
mal condition 2: Go
to step 5.
4 CHECK CATALYTIC CONVERTER. Is the catalytic converter dam-
aged?
Replace the cata-
lytic converter.
<Ref. to EC(STI)-
5, Front Catalytic
Converter.>
Go to step 5.
5 CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 6.
Step Check Yes No
EN-06668
1
0
10 sec/div
REAR OXYGEN
SENSOR VOLTAGE
(V)
EN-06669
1
0
10 sec/div
REAR OXYGEN
SENSOR VOLTAGE
(V)
EN-06670
1
0
10 sec/div
REAR OXYGEN
SENSOR VOLTAGE
(V)
15WRX_STI_US_EN.book 225 ージ 20  
EN(STI)(diag)-226
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
6 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM connector and rear oxygen sensor con-
nector.
Connector & terminal
(B136) No. 20 — (T6) No. 3:
(B135) No. 30 — (T6) No. 4:
Is the resistance less than 1 Ω? Go to step 7. Repair the harness
and connector.
NOTE:
Repair the follow-
ing locations.
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
coupling connector
7 CHECK REAR OXYGEN SENSOR SHIELD.
1) Turn the ignition switch to OFF.
2) Expose the rear oxygen sensor connector
body side harness sensor shield.
3) Measure the resistance between sensor
shield and chassis ground.
Is the resistance less than 1 Ω? Go to step 8. Repair the open
circuit of rear oxy-
gen sensor har-
ness.
8 CHECK ENGINE OIL AMOUNT AND EX-
HAUST GAS.
1) Check the engine oil amount. <Ref. to
LU(STI)-11, INSPECTION, Engine Oil.>
2) Check exhaust gas during idling.
Does the engine oil amount
drop or white smoke emit from
the muffler?
Check the engine,
and repair the
defective part.
<Ref. to ME(STI)-
107, INSPEC-
TION, Engine
Trouble in Gen-
eral.>
After repairing the
engine, replace the
catalytic con-
verter. <Ref. to
EX(STI)-7, Center
Exhaust Pipe.>
After the catalytic
converter is
replaced, perform
step 2 to check the
normal waveform
is displayed, and
then exit the proce-
dure.
Go to step 9.
9 CHECK IGNITION SYSTEM.
1) Check the spark plug. <Ref. to IG(STI)-5,
INSPECTION, Spark Plug.>
2) Check the status of the ignition coil connec-
tor and the spark plug terminal.
Is there any fault in the ignition
system?
After repairing the
ignition system,
replace the cata-
lytic converter.
<Ref. to EX(STI)-7,
Center Exhaust
Pipe.>
After the catalytic
converter is
replaced, perform
step 2 to check the
normal waveform
is displayed, and
then exit the proce-
dure.
Go to step 10.
Step Check Yes No
15WRX_STI_US_EN.book 226 ージ 20  
EN(STI)(diag)-227
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
10 CHECK FUEL SYSTEM.
1) Refer to and check the items in “Insufficient
fuel supply to fuel injector” (except for “a. Fuel
pump does not operate.”) and “Leakage or blow
out of fuel”. <Ref. to FU(STI)-100, INSPEC-
TION, Fuel System Trouble in General.>
2) Check throttle body. <Ref. to FU(STI)-15,
INSPECTION, Throttle Body.>
3) Check intake manifold. <Ref. to FU(STI)-32,
INSPECTION, Intake Manifold.>
Is there any fault in the fuel sys-
tem?
After repairing the
fuel system,
replace the cata-
lytic converter.
<Ref. to EX(STI)-7,
Center Exhaust
Pipe.>
After the catalytic
converter is
replaced, perform
step 2 to check the
normal waveform
is displayed, and
then exit the proce-
dure.
Go to step 11.
11 CHECK DTC. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
After checking the
DTC, replace the
catalytic con-
verter. <Ref. to
EX(STI)-7, Center
Exhaust Pipe.>
After the catalytic
converter is
replaced, perform
step 2 to check the
normal waveform
is displayed, and
then exit the proce-
dure.
Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
Step Check Yes No
15WRX_STI_US_EN.book 227 ージ 20  
EN(STI)(diag)-228
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CM:DTC P0441 EVAPORATIVE EMISSION CONT. SYS. INCORRECT PURGE
FLOW
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-119, DTC P0441 EVAPORATIVE EMISSION CONT. SYS.
INCORRECT PURGE FLOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK PURGE CONTROL SOLENOID
VALVE.
Operate the purge control solenoid valve using
the Subaru Select Monitor.
NOTE:
For detailed procedures, refer to “System Oper-
ation Check Mode”. <Ref. to EN(STI)(diag)-60,
System Operation Check Mode.>
Does the purge control sole-
noid valve operate?
Go to step 3. Replace the purge
control solenoid
valve. <Ref. to
EC(STI)-22, Purge
Control Solenoid
Valve.>
3 CHECK EVAPORATIVE EMISSION CON-
TROL SYSTEM LINE.
1) Turn the ignition switch to OFF.
2) Make sure that the delivery mode fuse is
removed.
Are there holes, cracks, clog-
ging, or disconnection, miscon-
nection of hoses or pipes in
evaporative emission control
system?
Repair or replace
the hoses or pipes.
Repair the poor
contact of ECM
connector.
15WRX_STI_US_EN.book 228 ージ 20  
EN(STI)(diag)-229
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CN:DTC P0451 EVAPORATIVE EMISSION SYSTEM PRESSURE SENSOR/
SWITCH RANGE/PERFORMANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-121, DTC P0451 EVAPORATIVE EMISSION SYSTEM
PRESSURE SENSOR/SWITCH RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Cri-
teria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK CURRENT DATA.
1) Turn the ignition switch to ON (engine OFF).
2) Using the Subaru Select Monitor or general
scan tool, read the value in «Atmosphere Pres-
sure» and «Mani. Absolute Pressure», and
compare them with the actual atmospheric
pressure.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
To read the actual atmospheric pressure,
connect the Subaru Select Monitor or general
scan tool to the other known good vehicle.
Is the difference with the actual
atmospheric pressure 3.3 kPa
(24.5 mmHg, 1 inHg) or more?
Replace the part
that showed larger
deviation from the
actual atmospheric
pressure than the
other.
If deviations in
value for «Atmo-
sphere Pressure»
is larger: Replace
the leak check
valve assembly.
<Ref. to EC(STI)-
30, Leak Check
Valve Assembly.>
If deviations in
value for «Mani.
Absolute Pres-
sure» is larger:
Replace the mani-
fold absolute pres-
sure sensor. <Ref.
to FU(STI)-41,
Manifold Absolute
Pressure Sensor.>
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
15WRX_STI_US_EN.book 229 ージ 20  
EN(STI)(diag)-230
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CO:DTC P0452 EVAPORATIVE EMISSION SYSTEM PRESSURE SENSOR/
SWITCH LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-123, DTC P0452 EVAPORATIVE EMISSION SYSTEM
PRESSURE SENSOR/SWITCH LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
B97
B83
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
B135B:
B136C:
B137D:
EN-10868
20
15
16
18
R1B97
19
17
*
*
B83
J/C
*
3
4
R400
1234
5678
R400
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
D27
5
1
6
7
8
B30
B4
B22
C21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
VACUUM PUMP
MAIN RELAY
BATTERY
FUSE HOLDER
LEAK CHECK VALVE ASSY
SWITCHING VALVE
PRESSURE SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 230 ージ 20  
EN(STI)(diag)-231
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Turn the ignition switch to ON.
2) Read the value of «Atmosphere Pressure»
using the Subaru Select Monitor or a general
scan tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value in «Atmosphere
Pressure» 34 kPa (255 mmHg,
10 inHg) or less?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK POWER SUPPLY OF LEAK CHECK
VALVE ASSEMBLY.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the leak
check valve assembly.
3) Turn the ignition switch to ON.
4) Measure the voltage between the leak
check valve assembly connector and chassis
ground.
Connector & terminal
(R400) No. 6 (+) — Chassis ground (–):
Is the voltage 4.5 V or more? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and the leak check
valve assembly
connector
Poor contact of
ECM connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 21 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 4. Repair the short
circuit to ground in
harness between
ECM connector
and leak check
valve assembly
connector.
4 CHECK FOR POOR CONTACT.
Check for poor contact of leak check valve
assembly connector.
Is there poor contact in the leak
check valve assembly connec-
tor?
Repair the poor
contact in the leak
check valve
assembly connec-
tor.
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
15WRX_STI_US_EN.book 231 ージ 20  
EN(STI)(diag)-232
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CP:DTC P0453 EVAPORATIVE EMISSION SYSTEM PRESSURE SENSOR/
SWITCH HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-124, DTC P0453 EVAPORATIVE EMISSION SYSTEM
PRESSURE SENSOR/SWITCH HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
B97
B83
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
B135B:
B136C:
B137D:
EN-10868
20
15
16
18
R1B97
19
17
*
*
B83
J/C
*
3
4
R400
1234
5678
R400
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
D27
5
1
6
7
8
B30
B4
B22
C21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
VACUUM PUMP
MAIN RELAY
BATTERY
FUSE HOLDER
LEAK CHECK VALVE ASSY
SWITCHING VALVE
PRESSURE SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 232 ージ 20  
EN(STI)(diag)-233
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Turn the ignition switch to ON.
2) Read the value of «Atmosphere Pressure»
using the Subaru Select Monitor or a general
scan tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value in «Atmosphere
Pressure» 125 kPa (938
mmHg, 36.9 inHg) or more?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
the leak check valve assembly.
3) Measure the resistance of harness between
ECM connector and the leak check valve
assembly connector.
Connector & terminal
(B136) No. 21 — (R400) No. 7:
(B135) No. 30 — (R400) No. 8:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and the leak check
valve assembly
connector
Poor contact of
coupling connector
Poor contact of
joint connector
3 CHECK FOR POOR CONTACT.
Check for poor contact of ECM and the leak
check valve assembly connector.
Is there poor contact in ECM
and the leak check valve
assembly connector?
Repair the poor
contact of ECM
and the leak check
valve assembly
connector.
Go to step 4.
4 CHECK LEAK CHECK VALVE ASSEMBLY.
Check the pressure sensor of the leak check
valve assembly. <Ref. to EC(STI)-47, CHECK
PRESSURE SENSOR, INSPECTION, Leak
Check Valve Assembly.>
Is the pressure sensor of the
leak check valve assembly OK?
Repair the short
circuit to power in
harness between
ECM connector
and leak check
valve assembly
connector.
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
15WRX_STI_US_EN.book 233 ージ 20  
EN(STI)(diag)-234
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CQ:DTC P0455 EVAPORATIVE EMISSION SYSTEM LEAK DETECTED (LARGE
LEAK)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-125, DTC P0455 EVAPORATIVE EMISSION SYSTEM
LEAK DETECTED (LARGE LEAK), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Fuel odor
There is a hole of more than 1.0 mm (0.04 in) dia. in evaporation system or fuel tank.
Fuel filler cap loose or lost
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FUEL FILLER CAP.
1) Turn the ignition switch to OFF.
2) Check the fuel filler cap.
NOTE:
The DTC is stored in memory if fuel filler cap is
or was loose or if the cap chain has caught while
tightening.
Is the fuel filler cap tightened
securely?
Go to step 2. Tighten fuel filler
cap securely.
2 CHECK FUEL FILLER CAP. Is the fuel filler cap genuine? Go to step 3. Replace with a
genuine fuel filler
cap.
3 CHECK FUEL FILLER PIPE GASKET. Is there any damage to the seal
between fuel filler cap and fuel
filler pipe?
Repair or replace
the fuel filler cap
and fuel filler pipe.
<Ref. to FU(STI)-
77, Fuel Filler
Pipe.>
Go to step 4.
4 CHECK PURGE CONTROL SOLENOID
VALVE.
Check air-tightness of the purge control sole-
noid valve. <Ref. to EC(STI)-23, INSPECTION,
Purge Control Solenoid Valve.>
Is the purge control solenoid
valve OK?
Go to step 5. Replace the purge
control solenoid
valve. <Ref. to
EC(STI)-22, Purge
Control Solenoid
Valve.>
5 CHECK EVAPORATIVE EMISSION CON-
TROL SYSTEM LINE.
Are there holes on the evapora-
tion line?
Repair or replace
the evaporation
line. <Ref. to
FU(STI)-94, Fuel
Delivery, Return
and Evaporation
Lines.>
Go to step 6.
6 CHECK CANISTER. Are there holes on the canis-
ter?
Replace the canis-
ter. <Ref. to
EC(STI)-7, Canis-
ter.>
Go to step 7.
7 CHECK LEAK CHECK VALVE ASSEMBLY. Are there damage or holes on
the leak check valve assembly?
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
Go to step 8.
15WRX_STI_US_EN.book 234 ージ 20  
EN(STI)(diag)-235
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CR:DTC P0456 EVAPORATIVE EMISSION CONTROL SYSTEM LEAK DETECT-
ED (VERY SMALL LEAK)
NOTE:
For the diagnostic procedure, refer to DTC P0455. <Ref. to EN(STI)(diag)-234, DTC P0455 EVAPORATIVE
EMISSION SYSTEM LEAK DETECTED (LARGE LEAK), Diagnostic Procedure with Diagnostic Trouble
Code (DTC).>
8 CHECK FUEL TANK.
Remove the fuel tank. <Ref. to FU(STI)-67, Fuel
Tank.>
Are there damage or holes on
the fuel tank?
Repair or replace
the fuel tank. <Ref.
to FU(STI)-67,
Fuel Tank.>
Go to step 9.
9 CHECK ANY OTHER MECHANICAL TROU-
BLE IN EVAPORATIVE EMISSION CON-
TROL SYSTEM.
Are there holes, cracks, clog-
ging, or disconnection, miscon-
nection of hoses or pipes in
evaporative emission control
system?
Repair or replace
the hoses or pipes.
Repair the poor
contact of ECM
connector.
Step Check Yes No
15WRX_STI_US_EN.book 235 ージ 20  
EN(STI)(diag)-236
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CS:DTC P0458 EVAPORATIVE EMISSION SYSTEM PURGE CONTROL VALVE
CIRCUIT LOW
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-131, DTC P0458 EVAPORATIVE EMISSION SYSTEM
PURGE CONTROL VALVE CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK OUTPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 6 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 2. Go to step 3.
E4
12
E52
B137
44
EN-10869
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
19
18
20 21
22
23
26
24
25
27
28 29
30 31
98
15
1413121110
17
16
1234567
B137
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
1
48
11
2
6
E4
2
1
E52
B21 E2
15
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
PURGE CONTROL
SOLENOID VALVE 2
PURGE CONTROL
SOLENOID VALVE 1
MAIN RELAY
BATTERY
FUSE HOLDER
15WRX_STI_US_EN.book 236 ージ 20  
EN(STI)(diag)-237
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.
Is there poor contact of ECM
connector?
Repair the poor
contact of ECM
connector.
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary open or
short circuit of har-
ness or temporary
poor contact of
connector may be
the cause.
3 CHECK POWER SUPPLY TO PURGE CON-
TROL SOLENOID VALVE CONNECTOR.
Measure the voltage between purge control
solenoid valve connector and engine ground.
Connector & terminal
(E4) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 4. Repair the power
supply circuit.
4 CHECK HARNESS BETWEEN ECM AND
PURGE CONTROL SOLENOID VALVE CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
purge control solenoid valve.
3) Measure the resistance between the purge
control solenoid valve connector and engine
ground.
Connector & terminal
(E4) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
ECM connector
and purge control
solenoid valve con-
nector.
5 CHECK HARNESS BETWEEN ECM AND
PURGE CONTROL SOLENOID VALVE CON-
NECTOR.
Measure the resistance of harness between
ECM connector and purge control solenoid
valve connector.
Connector & terminal
(B137) No. 6 — (E4) No. 2:
Is the resistance less than 1 Ω? Go to step 6. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and purge control
solenoid valve
connector
Poor contact of
coupling connector
6 CHECK PURGE CONTROL SOLENOID
VALVE.
1) Remove the purge control solenoid valve.
2) Measure the resistance between purge con-
trol solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance 10 — 100 Ω? Repair the poor
contact of purge
control solenoid
valve connector.
Replace the purge
control solenoid
valve. <Ref. to
EC(STI)-22, Purge
Control Solenoid
Valve.>
Step Check Yes No
15WRX_STI_US_EN.book 237 ージ 20  
EN(STI)(diag)-238
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CT:DTC P0459 EVAPORATIVE EMISSION SYSTEM PURGE CONTROL VALVE
CIRCUIT HIGH
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-132, DTC P0459 EVAPORATIVE EMISSION SYSTEM
PURGE CONTROL VALVE CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
PURGE CONTROL SOLENOID VALVE CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
purge control solenoid valve.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 6 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and purge
control solenoid
valve connector.
Go to step 2.
E4
12
E52
B137
44
EN-10869
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
19
18
20 21
22
23
26
24
25
27
28 29
30 31
98
15
1413121110
17
16
1234567
B137
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
1
48
11
2
6
E4
2
1
E52
B21 E2
15
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
PURGE CONTROL
SOLENOID VALVE 2
PURGE CONTROL
SOLENOID VALVE 1
MAIN RELAY
BATTERY
FUSE HOLDER
15WRX_STI_US_EN.book 238 ージ 20  
EN(STI)(diag)-239
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK PURGE CONTROL SOLENOID
VALVE.
1) Turn the ignition switch to OFF.
2) Measure the resistance between purge con-
trol solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance less than 1 Ω? Replace the purge
control solenoid
valve. <Ref. to
EC(STI)-22, Purge
Control Solenoid
Valve.>
Repair the poor
contact of ECM
connector.
Step Check Yes No
15WRX_STI_US_EN.book 239 ージ 20  
EN(STI)(diag)-240
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CU:DTC P0461 FUEL LEVEL SENSOR “A” CIRCUIT RANGE/PERFORMANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-133, DTC P0461 FUEL LEVEL SENSOR “A” CIRCUIT
RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
CV:DTC P0462 FUEL LEVEL SENSOR “A” CIRCUIT LOW
NOTE:
For the diagnostic procedure, refer to DTC P0463. <Ref. to EN(STI)(diag)-241, DTC P0463 FUEL LEVEL
SENSOR “A” CIRCUIT HIGH, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Replace the fuel
level sensor and
fuel sub level sen-
sor. <Ref. to
FU(STI)-84, Fuel
Level Sensor.>
<Ref. to FU(STI)-
85, Fuel Sub Level
Sensor.>
15WRX_STI_US_EN.book 240 ージ 20  
EN(STI)(diag)-241
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CW:DTC P0463 FUEL LEVEL SENSOR “A” CIRCUIT HIGH
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-135, DTC P0463 FUEL LEVEL SENSOR “A” CIRCUIT
HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is DTC P0462 or P0463 dis-
played on the Subaru Select
Monitor?
Check the combi-
nation meter. <Ref.
to IDI(diag)-2,
Basic Diagnostic
Procedure.>
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
15WRX_STI_US_EN.book 241 ージ 20  
EN(STI)(diag)-242
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CX:DTC P04AC EVAP SYSTEM PURGE CONTROL VALVE "B" CIRCUIT LOW
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-136, DTC P04AC EVAP SYSTEM PURGE CONTROL
VALVE "B" CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK OUTPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 15 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 2. Go to step 3.
E4
12
E52
B137
44
EN-10869
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
19
18
20 21
22
23
26
24
25
27
28 29
30 31
98
15
1413121110
17
16
1234567
B137
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
1
48
11
2
6
E4
2
1
E52
B21 E2
15
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
PURGE CONTROL
SOLENOID VALVE 2
PURGE CONTROL
SOLENOID VALVE 1
MAIN RELAY
BATTERY
FUSE HOLDER
15WRX_STI_US_EN.book 242 ージ 20  
EN(STI)(diag)-243
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.
Is there poor contact of ECM
connector?
Repair the poor
contact of ECM
connector.
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary open or
short circuit of har-
ness or temporary
poor contact of
connector may be
the cause.
3 CHECK POWER SUPPLY TO PURGE CON-
TROL SOLENOID VALVE 2 CONNECTOR.
Measure the voltage between purge control
solenoid valve 2 connector and engine ground.
Connector & terminal
(E52) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 4. Repair the power
supply circuit.
4 CHECK HARNESS BETWEEN ECM AND
PURGE CONTROL SOLENOID VALVE 2
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
purge control solenoid valve 2.
3) Measure the resistance between the purge
control solenoid valve 2 connector and engine
ground.
Connector & terminal
(E52) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the ground
short circuit of har-
ness between
ECM connector
and purge control
solenoid valve 2
connector.
5 CHECK HARNESS BETWEEN ECM AND
PURGE CONTROL SOLENOID VALVE 2
CONNECTOR.
Measure the resistance of harness between
ECM connector and purge control solenoid
valve 2 connector.
Connector & terminal
(B137) No. 15 — (E52) No. 2:
Is the resistance less than 1 Ω? Go to step 6. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and purge control
solenoid valve 2
connector
Poor contact of
coupling connector
6 CHECK PURGE CONTROL SOLENOID
VALVE 2.
1) Remove the purge control solenoid valve 2.
2) Measure the resistance between purge con-
trol solenoid valve 2 terminals.
Terminals
No. 1 — No. 2:
Is the resistance 10 — 100 Ω? Repair the poor
contact of the
purge control sole-
noid valve 2 con-
nector.
Replace the purge
control solenoid
valve 2. <Ref. to
EC(STI)-22, Purge
Control Solenoid
Valve.>
Step Check Yes No
15WRX_STI_US_EN.book 243 ージ 20  
EN(STI)(diag)-244
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CY:DTC P04AD EVAP SYSTEM PURGE CONTROL VALVE "B" CIRCUIT HIGH
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-137, DTC P04AD EVAP SYSTEM PURGE CONTROL
VALVE "B" CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
PURGE CONTROL SOLENOID VALVE 2
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
purge control solenoid valve 2.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 15 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and purge control
solenoid valve 2
connector.
Go to step 2.
E4
12
E52
B137
44
EN-10869
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
19
18
20 21
22
23
26
24
25
27
28 29
30 31
98
15
1413121110
17
16
1234567
B137
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
1
48
11
2
6
E4
2
1
E52
B21 E2
15
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
PURGE CONTROL
SOLENOID VALVE 2
PURGE CONTROL
SOLENOID VALVE 1
MAIN RELAY
BATTERY
FUSE HOLDER
15WRX_STI_US_EN.book 244 ージ 20  
EN(STI)(diag)-245
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK PURGE CONTROL SOLENOID
VALVE 2.
1) Turn the ignition switch to OFF.
2) Measure the resistance between purge con-
trol solenoid valve 2 terminals.
Terminals
No. 1 — No. 2:
Is the resistance less than 1 Ω? Replace the purge
control solenoid
valve 2. <Ref. to
EC(STI)-22, Purge
Control Solenoid
Valve.>
Repair the poor
contact of ECM
connector.
Step Check Yes No
15WRX_STI_US_EN.book 245 ージ 20  
EN(STI)(diag)-246
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
CZ:DTC P04DB CRANKCASE VENTILATION SYSTEM DISCONNECTED
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-138, DTC P04DB CRANKCASE VENTILATION SYSTEM
DISCONNECTED, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK BLOW-BY HOSE.
Check the blow-by hose condition.
Is there any disconnection or
crack in blow-by hose?
Install or replace
the blow-by hose.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
PCV HOSE ASSEMBLY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the ECM
and PCV hose assembly.
3) Measure the resistance of harness between
ECM connector and PCV hose assembly con-
nector.
Connector & terminal
(B137) No. 12 — (E80) No. 2:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and PCV hose as-
sembly connector
Poor contact of
coupling connector
E2B21
45
E87
1
2
E80
2
1
EN-10870
E80
12
E87
B137
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
19
18
20 21
22
23
26
24
25
27
28 29
30 31
98
15
1413121110
17
16
1234567
B137
12
ECM
LEAK DIAGNOSIS
CONNECTOR 1
LEAK DIAGNOSIS
CONNECTOR 2
15WRX_STI_US_EN.book 246 ージ 20  
EN(STI)(diag)-247
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
3 CHECK HARNESS BETWEEN ECM AND
PCV HOSE ASSEMBLY CONNECTOR.
Measure the resistance between PCV hose
assembly connector and chassis ground.
Connector & terminal
(B137) No. 12 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 4. Repair the short
circuit to ground in
harness between
ECM connector
and PCV hose
assembly connec-
tor.
4 CHECK HARNESS BETWEEN LEAK DIAG-
NOSIS CONNECTORS.
Measure the resistance of harness between
leak diagnosis connectors.
Connector & terminal
(E80) No. 1 — (E87) No. 1:
Is the resistance less than 1 Ω? Go to step 5. Repair the open
circuit in the wiring
harness between
leak diagnosis
connectors.
5 CHECK GROUND CIRCUIT OF PCV HOSE
ASSEMBLY.
Measure the resistance of harness between
PCV hose assembly connector and engine
ground.
Connector & terminal
(E87) No. 2 — Engine ground:
Is the resistance less than 5 Ω? Go to step 6. Repair the open
circuit in harness
between PCV hose
assembly connec-
tor and engine
ground.
6 CHECK PCV HOSE ASSEMBLY.
Measure the resistance between terminals of
each leak diagnosis connector.
Terminals
No. 1 — No. 2:
Is the resistance less than 1 Ω
at all measurement?
Repair the poor
contact of ECM
and PCV hose
assembly connec-
tor.
Replace the PCV
hose assembly.
<Ref. to EC(STI)-
49, PCV Hose
Assembly.>
Step Check Yes No
15WRX_STI_US_EN.book 247 ージ 20  
EN(STI)(diag)-248
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DA:DTC P0500 VEHICLE SPEED SENSOR “A”
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-139, DTC P0500 VEHICLE SPEED SENSOR “A”, Diagnos-
tic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK DTC OF VDC.
Check DTC of VDC.
Is DTC of VDC displayed? Perform the diag-
nosis according to
DTC. <Ref. to
VDC(diag)-42, List
of Diagnostic Trou-
ble Code (DTC).>
Repair the poor
contact of ECM
connector.
15WRX_STI_US_EN.book 248 ージ 20  
EN(STI)(diag)-249
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DB:DTC P0506 IDLE AIR CONTROL SYSTEM RPM LOWER THAN EXPECTED
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-140, DTC P0506 IDLE AIR CONTROL SYSTEM RPM LOW-
ER THAN EXPECTED, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Hard to start the engine.
Engine does not start.
Improper idling
Engine stalls.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK AIR CLEANER ELEMENT.
1) Turn the ignition switch to OFF.
2) Check the air cleaner element.
Is there excessive clogging on
air cleaner element?
Replace the air
cleaner element.
<Ref. to IN(STI)-8,
Air Cleaner Ele-
ment.>
Go to step 3.
3 CHECK ELECTRONIC THROTTLE CON-
TROL.
1) Remove the electronic throttle control. <Ref.
to FU(STI)-15, REMOVAL, Throttle Body.>
2) Check the electronic throttle control.
Are foreign matter found inside
electronic throttle control?
Remove foreign
matter from elec-
tronic throttle con-
trol.
Perform the diag-
nosis of DTC
P2101. <Ref. to
EN(STI)(diag)-
344, DTC P2101
THROTTLE
ACTUATOR CON-
TROL MOTOR
CIRCUIT RANGE/
PERFORMANCE,
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
15WRX_STI_US_EN.book 249 ージ 20  
EN(STI)(diag)-250
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DC:DTC P0507 IDLE AIR CONTROL SYSTEM RPM HIGHER THAN EXPECTED
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-141, DTC P0507 IDLE AIR CONTROL SYSTEM RPM
HIGHER THAN EXPECTED, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine keeps running at higher speed than specified idle speed.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK AIR INTAKE SYSTEM.
1) Start and idle the engine.
2) Check the following items.
Loose installation of intake manifold and
throttle body
Cracks of intake manifold gasket and throttle
body gasket
Disconnection of vacuum hoses
Is there any fault in air intake
system?
Repair air suction
and leaks.
Go to step 3.
3 CHECK ELECTRONIC THROTTLE CON-
TROL.
1) Turn the ignition switch to OFF.
2) Remove the electronic throttle control. <Ref.
to FU(STI)-15, REMOVAL, Throttle Body.>
3) Check the electronic throttle control.
Are foreign matter found inside
electronic throttle control?
Remove foreign
matter from elec-
tronic throttle con-
trol.
Perform the diag-
nosis of DTC
P2101. <Ref. to
EN(STI)(diag)-
344, DTC P2101
THROTTLE
ACTUATOR CON-
TROL MOTOR
CIRCUIT RANGE/
PERFORMANCE,
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
15WRX_STI_US_EN.book 250 ージ 20  
EN(STI)(diag)-251
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DD:DTC P050A COLD START IDLE AIR CONTROL SYSTEM PERFORMANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-142, DTC P050A COLD START IDLE AIR CONTROL SYS-
TEM PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine keeps running at higher speed than specified idle speed.
Engine keeps running at a lower speed than the specified idle speed.
Engine stalls.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 251 ージ 20  
EN(STI)(diag)-252
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
10
B220
11
B550
216
51
52
53
54
E2
B21
48
2
1
E5
B134
10
11
12
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B134
8
5
6
10 11 12 13 14 15
72134
16
30
19 20 22
28 29
9
17
18 2521 23 24
3231
26 27
33 34
EN-10855
2
1
E16
2
1
E6
2
1
E17
13
E5
E6
E16
E17
21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
FUEL INJECTOR No. 4
FUEL INJECTOR No. 3
FUEL INJECTOR No. 2
FUEL INJECTOR No. 1
BATTERY
FUSE HOLDER
MAIN RELAY
15WRX_STI_US_EN.book 252 ージ 20  
EN(STI)(diag)-253
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK ENGINE OIL. Is there a proper amount of
engine oil?
Go to step 3. Replace engine oil.
<Ref. to LU(STI)-
11, REPLACE-
MENT, Engine
Oil.>
3 CHECK EXHAUST SYSTEM. Are there holes or loose bolts
on exhaust system?
Repair the exhaust
system.
Go to step 4.
28
36
35
40
34
A3
A6
D1
D3
A4
B225
14
17
15
16
B122
J/C
*
*
B550
216
418
B220
1011
E2
B21
25
39
38
6
24
E57
B134A:
B135B:
B136C:
B137D:
A1
A2
A29
A28
6
5
4
3
2
1
A19
A18
C4
B17
B7
B225B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
321654
E57
B122
34
56
12
78
EN-10861
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
ECM
SBF-7
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
*
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
ELECTRONIC THROTTLE
CONTROL
MAIN
RELAY
FUSE
HOLDER
ELECTRONIC THROTTLE
CONTROL RELAY
15WRX_STI_US_EN.book 253 ージ 20  
EN(STI)(diag)-254
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
4 CHECK AIR INTAKE SYSTEM. Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
Go to step 5.
5 CHECK FUEL PRESSURE.
WARNING:
Place “NO OPEN FLAMES” signs near the
working area.
CAUTION:
Be careful not to spill fuel.
Measure the fuel pressure while disconnecting
pressure regulator vacuum hose from intake
manifold. <Ref. to ME(STI)-25, INSPECTION,
Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze the
fuel return hose 2 to 3 times, then measure fuel
pressure again.
Is the measured value 284 —
314 kPa (2.9 — 3.2 kg/cm
2
, 41
— 46 psi)?
Go to step 6. Check the fuel
pump and fuel
delivery line. <Ref.
to FU(STI)-83,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-99,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
6 CHECK FUEL PRESSURE.
After connecting the pressure regulator vacuum
hose, measure fuel pressure. <Ref. to ME(STI)-
25, INSPECTION, Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure fuel
pressure again.
If the measured value at this step is out of
specification, check or replace pressure regula-
tor and pressure regulator vacuum hose.
Is the measured value 230 —
260 kPa (2.4 — 2.7 kg/cm
2
, 33
— 38 psi)?
Go to step 7. Check the fuel
pump and fuel
delivery line. <Ref.
to FU(STI)-83,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-99,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
7 CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm up completely.
2) Read the value of «Coolant Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Coolant Temp.»
75°C (167°F) or more?
Go to step 8. Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(STI)-33,
Engine Coolant
Temperature Sen-
sor.>
Step Check Yes No
15WRX_STI_US_EN.book 254 ージ 20  
EN(STI)(diag)-255
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
8 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Read the value of «Mass Air Flow» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Mass Air
Flow» 2.0 — 5.0 g/s (0.26 —
0.66 lb/m)?
Go to step 9. Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
9 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Open the front hood.
6) Measure the ambient temperature.
7) Read the value of «Intake Air Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Subtract ambient temperature
from «Intake Air Temp.». Is the
obtained value –10 — 50°C (–18
— 90°F)?
Go to step 10. Check the mass air
flow and intake air
temperature sen-
sor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
10 CHECK OUTPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground on faulty cylinders.
Connector & terminal
#1 (B134) No. 10 (+) — Chassis ground (–):
#2 (B134) No. 11 (+) — Chassis ground (–):
#3 (B134) No. 12 (+) — Chassis ground (–):
#4 (B134) No. 13 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 15. Go to step 11.
Step Check Yes No
15WRX_STI_US_EN.book 255 ージ 20  
EN(STI)(diag)-256
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
11 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector
on faulty cylinders.
3) Measure the resistance between fuel injec-
tor connector and engine ground on faulty cylin-
ders.
Connector & terminal
#1 (E5) No. 2 — Engine ground:
#2 (E16) No. 2 — Engine ground:
#3 (E6) No. 2 — Engine ground:
#4 (E17) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 12. Repair the short
circuit to ground in
harness between
ECM connector
and fuel injector
connector.
12 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
Measure the resistance of harness between
ECM connector and fuel injector connector on
faulty cylinders.
Connector & terminal
#1 (B134) No. 10 — (E5) No. 2:
#2 (B134) No. 11 — (E16) No. 2:
#3 (B134) No. 12 — (E6) No. 2:
#4 (B134) No. 13 — (E17) No. 2:
Is the resistance less than 1 Ω? Go to step 13. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and fuel injector
connector
Poor contact of
coupling connector
13 CHECK FUEL INJECTOR.
Measure the resistance between fuel injector
terminals on faulty cylinder.
Terminals
No. 1 — No. 2:
Is the resistance 5 — 20 Ω? Go to step 14. Replace the faulty
fuel injector. <Ref.
to FU(STI)-43,
Fuel Injector.>
14 CHECK POWER SUPPLY LINE.
1) Turn the ignition switch to ON.
2) Measure the voltage between fuel injector
and engine ground on faulty cylinders.
Connector & terminal
#1 (E5) No. 1 (+) — Engine ground (–):
#2 (E16) No. 1 (+) — Engine ground (–):
#3 (E6) No. 1 (+) — Engine ground (–):
#4 (E17) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Repair the poor
contact of all con-
nectors in fuel
injector circuit.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
the main relay con-
nector and fuel in-
jector connector on
faulty cylinders
Poor contact of
coupling connector
Poor contact of
main relay connec-
tor
15 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector
on faulty cylinders.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground on faulty cylinders.
Connector & terminal
#1 (B134) No. 10 (+) — Chassis ground (–):
#2 (B134) No. 11 (+) — Chassis ground (–):
#3 (B134) No. 12 (+) — Chassis ground (–):
#4 (B134) No. 13 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and fuel injector
connectors.
Go to step 16.
Step Check Yes No
15WRX_STI_US_EN.book 256 ージ 20  
EN(STI)(diag)-257
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
16 CHECK FUEL INJECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between fuel injec-
tor terminals on faulty cylinder.
Terminals
No. 1 — No. 2:
Is the resistance 5 — 20 Ω? Go to step 17. Replace the faulty
fuel injector. <Ref.
to FU(STI)-43,
Fuel Injector.>
17 CHECK INSTALLATION OF CAMSHAFT PO-
SITION SENSOR/CRANKSHAFT POSITION
SENSOR.
Is the camshaft position sensor
or crankshaft position sensor
loosely installed?
Tighten the cam-
shaft position sen-
sor or crankshaft
position sensor.
<Ref. to FU(STI)-
35, Camshaft Posi-
tion Sensor.> <Ref.
to FU(STI)-34,
Crankshaft Posi-
tion Sensor.>
Go to step 18.
18 CHECK CRANK SPROCKET.
Remove the timing belt cover. <Ref. to ME(STI)-
50, REMOVAL, Timing Belt Cover.>
Is the crank sprocket rusted or
does it have broken teeth?
Replace the crank
sprocket. <Ref. to
ME(STI)-61, Crank
Sprocket.>
Go to step 19.
19 CHECK INSTALLATION CONDITION OF
TIMING BELT.
Turn the crankshaft, and align alignment mark
on crank sprocket with alignment mark on cylin-
der block.
ST 499987500 CRANKSHAFT
SOCKET
Is the timing belt dislocated
from its proper position?
Repair the installa-
tion condition of
timing belt. <Ref. to
ME(STI)-51, Tim-
ing Belt.>
Go to step 20.
20 CHECK ELECTRONIC THROTTLE CON-
TROL RELAY.
1) Turn the ignition switch to OFF.
2) Remove the electronic throttle control relay.
3) Connect the battery to terminals No. 16 and
No. 17 of electronic throttle control relay.
4) Measure the resistance between electronic
throttle control relay terminals.
Terminals
No. 15 — No. 16:
Is the resistance less than 1 Ω? Go to step 21. Replace the elec-
tronic throttle con-
trol relay. <Ref. to
FU(STI)-60, Elec-
tronic Throttle
Control Relay.>
21 CHECK POWER SUPPLY OF ELECTRONIC
THROTTLE CONTROL RELAY.
Measure the voltage between electronic throttle
control relay connector and chassis ground.
Connector & terminal
(B225) No. 15 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 22. Repair the open or
ground short circuit
of power supply
circuit.
22 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY CONNECTOR.
1) Disconnect the connector from ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between electronic
throttle control relay connector and chassis
ground.
Connector & terminal
(B225) No. 17 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control relay con-
nector.
Go to step 23.
Step Check Yes No
15WRX_STI_US_EN.book 257 ージ 20  
EN(STI)(diag)-258
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
23 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between electronic
throttle control relay connector and chassis
ground.
Connector & terminal
(B225) No. 14 — Chassis ground:
(B225) No. 17 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 24. Repair the short
circuit to ground in
harness between
ECM connector
and electronic
throttle control
relay connector.
24 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY CONNECTOR.
Measure the resistance between ECM connec-
tor and electronic throttle control relay connec-
tor.
Connector & terminal
(B135) No. 7 — (B225) No. 14:
(B135) No. 17 — (B225) No. 17:
Is the resistance less than 1 Ω? Go to step 25. Repair the open
circuit in harness
between ECM con-
nector and elec-
tronic throttle
control relay con-
nector.
25 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
electronic throttle control.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 19 — Chassis ground:
(B134) No. 18 — Chassis ground:
(B134) No. 18 — (B136) No. 4:
(B134) No. 28 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 26. Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
26 CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Connect the connector to ECM.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(B57) No. 6 — Engine ground:
(B57) No. 4 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 27. Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
Replace the ECM if
defective. <Ref. to
FU(STI)-56,
Engine Control
Module (ECM).>
27 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Disconnect the connector from ECM.
2) Measure the resistance of harness between
ECM connector and electronic throttle control
connector.
Connector & terminal
(B134) No. 18 — (E57) No. 6:
(B134) No. 28 — (E57) No. 4:
(B134) No. 29 — (E57) No. 3:
Is the resistance less than 1 Ω? Go to step 28. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and electronic
throttle control
connector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 258 ージ 20  
EN(STI)(diag)-259
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
28 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Connect the connector to ECM.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 3 — Engine ground:
Is the resistance less than 5 Ω? Go to step 29. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
ECM connector
Poor contact of
coupling connector
29 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 6 (+) — Engine ground (–):
(E57) No. 4 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
Go to step 30.
30 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B134) No. 19 — (B134) No. 18:
(B134) No. 19 — (B134) No. 28:
Is the resistance 1 MΩ or
more?
Go to step 31. Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
31 CHECK SENSOR OUTPUT.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Read the value of «Main-Throttle Sensor»
using Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Main-Throttle
Sensor» 0.81 — 0.87 V?
Go to step 32. Repair the poor
contact of elec-
tronic throttle con-
trol connector.
Replace the elec-
tronic throttle con-
trol if defective.
<Ref. to FU(STI)-
15, Throttle Body.>
32 CHECK SENSOR OUTPUT.
Read the value of «Sub-Throttle Sensor» using
Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Sub-Throttle
Sensor» 1.64 — 1.70 V?
Go to step 33. Repair the poor
contact of elec-
tronic throttle con-
trol connector.
Replace the elec-
tronic throttle con-
trol if defective.
<Ref. to FU(STI)-
15, Throttle Body.>
Step Check Yes No
15WRX_STI_US_EN.book 259 ージ 20  
EN(STI)(diag)-260
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
33 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL MO-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
electronic throttle control.
3) Measure the resistance between ECM con-
nector and electronic throttle control connector.
Connector & terminal
(B134) No. 1 — (E57) No. 1:
(B134) No. 2 — (E57) No. 2:
Is the resistance less than 1 Ω? Go to step 34. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and electronic
throttle control
connector
Poor contact of
coupling connector
34 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL MO-
TOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 1 (+) — Engine ground (–):
(E57) No. 2 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
Go to step 35.
35 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL MO-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 1 — Engine ground:
(E57) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 36. Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
36 CHECK ELECTRONIC THROTTLE CON-
TROL MOTOR HARNESS.
Measure the resistance between electronic
throttle control connectors.
Connector & terminal
(E57) No. 1 — (E57) No. 2:
Is the resistance 1 MΩ or
more?
Go to step 37. Repair the short
circuit in harness
between ECM con-
nector and elec-
tronic throttle
control connector.
37 CHECK ELECTRONIC THROTTLE CON-
TROL GROUND CIRCUIT.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 3 — Chassis ground:
(B134) No. 4 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 3 — Chassis ground:
Is the resistance less than 5 Ω? Go to step 38. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
coupling connector
38 CHECK ELECTRONIC THROTTLE CON-
TROL.
Measure the resistance between electronic
throttle control terminals.
Terminals
No. 1 — No. 2:
Is the resistance 50 Ω or less? Go to step 39. Replace the elec-
tronic throttle con-
trol. <Ref. to
FU(STI)-15, Throt-
tle Body.>
Step Check Yes No
15WRX_STI_US_EN.book 260 ージ 20  
EN(STI)(diag)-261
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DE:DTC P050B COLD START IGNITION TIMING PERFORMANCE
NOTE:
For the diagnostic procedure, refer to DTC P050A. <Ref. to EN(STI)(diag)-251, DTC P050A COLD START
IDLE AIR CONTROL SYSTEM PERFORMANCE, Diagnostic Procedure with Diagnostic Trouble Code
(DTC).>
39 CHECK ELECTRONIC THROTTLE CON-
TROL.
Move the throttle valve to the fully open and fully
closed positions with fingers.
Check that the valve returns to the specified
position when releasing fingers.
Does the valve return to the
specified position? Standard
value: 3 mm (0.12 in) from fully
closed position
Repair the poor
contact of ECM
connector.
Replace the elec-
tronic throttle con-
trol. <Ref. to
FU(STI)-15, Throt-
tle Body.>
Step Check Yes No
15WRX_STI_US_EN.book 261 ージ 20  
EN(STI)(diag)-262
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DF:DTC P0512 STARTER REQUEST CIRCUIT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-145, DTC P0512 STARTER REQUEST CIRCUIT, Diagnos-
tic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 262 ージ 20  
EN(STI)(diag)-263
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
B23
12345
6789
10
B550
228
B136C:
B135B:
B14
1
M
B574C:
B572A:
B28B23
3
21
A7
C6
1
B106
1
3
2
B225
5
28
30
29
B225
31
39 38
36 37
B225
19 20 21 22 23 24 25 26 27 28 29 30
789
10 11 12 13 14 15 16 17 18
123 456
B574C:
11 12
34
13 14
56
15 16
78
17 18
10
9
12
B572A:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29
3231
1234
56
2726
33 34 35
B136C:
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
B575
123
456789
10 11
12 13 14 15 16 17 18 19 20 21 22
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B106
1
2
EN-10852
B14
1
B550
1024
41
42
44
B225
40
2
B34
B26
C16
C27
B576B575
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-6
STARTER CUT
RELAY
FUSE
HOLDER
BATTERY
MAIN SBF
IG RELAY 1
(PUSH BUTTON
START)
F/B No. 26
STARTER RELAY
(PUSH BUTTON START)
STARTER
RELAY
CLUTCH START SWITCH
F/B No. 21
KEYLESS
ACCESS CM
STARTER MOTOR
FUSE
HOLDER
15WRX_STI_US_EN.book 263 ージ 20  
EN(STI)(diag)-264
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK PUSH BUTTON IGNITION SWITCH.
Operate the push button ignition switch.
Does it operate smoothly with-
out catch?
Go to step 2. Replace the push
button ignition
switch. <Ref. to
SL-106, Push But-
ton Ignition
Switch.>
2 CHECK DTC.
1) Clear the memory using the Subaru Select
Monitor. <Ref. to EN(STI)(diag)-59, Clear Mem-
ory Mode.>
2) Start and idle the engine for three minutes
or more.
Is the same DTC as current
diagnosis output?
Go to step 3. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
3 CHECK HARNESS BETWEEN ECM AND
KEYLESS ACCESS CM.
1) Turn the ignition to OFF.
2) Disconnect the connector from ECM.
3) Turn the ignition to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 16 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power
supply in harness
between ECM con-
nector and keyless
access CM con-
nector.
Repair the poor
contact of ECM
connector.
15WRX_STI_US_EN.book 264 ージ 20  
EN(STI)(diag)-265
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DG:DTC P0560 SYSTEM VOLTAGE
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-146, DTC P0560 SYSTEM VOLTAGE, Diagnostic Trouble
Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
34
40
WP
OP
WP
OP
B72
B550
216
B550
1024
B220
11
12
10
13
B134A:
B135B:
B136C:
B137D:
A3
A6
D1
D3
A4
36
35
E2
B21
C30
C2
B13
D7
C1
B220 B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
14
B225
36 37
EN-10853
WP
OP
B72
7856
3412
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SBF-6
ECM
: WITHOUT PUSH BUTTON START
: WITH PUSH BUTTON START
IG RELAY 1
(PUSH BUTTON
START)
BATTERY
MAIN
RELAY
FUSE
HOLDER
FUSE
HOLDER
M/B No. 13
F/B No. 12
IGNITION
SWITCH
MAIN SBF
15WRX_STI_US_EN.book 265 ージ 20  
EN(STI)(diag)-266
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK INPUT SIGNAL OF ECM.
1) Turn the ignition switch to OFF.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 2 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the poor
contact of ECM
connector.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
MAIN FUSE BOX CONNECTOR.
1) Disconnect the connector from ECM.
2) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 2 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and battery termi-
nal.
3 CHECK FUSE NO. 13. Is the fuse blown out? Replace the fuse. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and battery
Poor contact of
ECM connector
Poor contact of
battery terminal
15WRX_STI_US_EN.book 266 ージ 20  
EN(STI)(diag)-267
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DH:DTC P0604 INTERNAL CONTROL MODULE RANDOM ACCESS MEMORY
(RAM) ERROR
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-147, DTC P0604 INTERNAL CONTROL MODULE RAN-
DOM ACCESS MEMORY (RAM) ERROR, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine does not start.
Engine stalls.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
DI: DTC P0605 INTERNAL CONTROL MODULE READ ONLY MEMORY (ROM)
ERROR
NOTE:
For the diagnostic procedure, refer to DTC P0606. <Ref. to EN(STI)(diag)-268, DTC P0606 CONTROL
MODULE PROCESSOR, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
15WRX_STI_US_EN.book 267 ージ 20  
EN(STI)(diag)-268
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DJ:DTC P0606 CONTROL MODULE PROCESSOR
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-149, DTC P0606 CONTROL MODULE PROCESSOR, Di-
agnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
321654
E57
B122
34
56
12
78
EN-10871
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B122
J/C
*
*
B550
216
B220
1110
B134A:
B136C:
B137D:
C4
D7
C1
A18
A19
1
2
3
4
5
6
A28
A29
A2
A1
E57
24
6
38
39
25
E2
B21
A4
D3
D1
A6
A3
36
35
40
34
28
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
*
SBF-7
ECM
ELECTRONIC THROTTLE
CONTROL
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
MAIN RELAY
FUSE HOLDER
15WRX_STI_US_EN.book 268 ージ 20  
EN(STI)(diag)-269
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DK:DTC P060A INTERNAL CONTROL MODULE MONITORING PROCESSOR
PERFORMANCE
NOTE:
For the diagnostic procedure, refer to DTC P0606. <Ref. to EN(STI)(diag)-268, DTC P0606 CONTROL
MODULE PROCESSOR, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
DL:DTC P060B INTERNAL CONTROL MODULE A/D PROCESSING PERFOR-
MANCE
NOTE:
For the diagnostic procedure, refer to DTC P0606. <Ref. to EN(STI)(diag)-268, DTC P0606 CONTROL
MODULE PROCESSOR, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
Step Check Yes No
1 CHECK INPUT VOLTAGE OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 1 (+) — Chassis ground (–):
(B137) No. 7 (+) — Chassis ground (–):
Is the voltage 10 — 13 V? Go to step 2. Repair the open or
ground short circuit
of power supply
circuit.
2 CHECK INPUT VOLTAGE OF ECM.
1) Start the engine.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 1 (+) — Chassis ground (–):
(B137) No. 7 (+) — Chassis ground (–):
Is the voltage 13 — 15 V? Go to step 3. Repair the open or
ground short circuit
of power supply
circuit.
3 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
electronic throttle control.
3) Measure the resistance of harness between
ECM connector and electronic throttle control
connector.
Connector & terminal
(B134) No. 19 — (E57) No. 5:
(B134) No. 29 — (E57) No. 3:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and electronic
throttle control
connector
Poor contact of
coupling connector
4 CHECK ECM GROUND HARNESS.
1) Connect all connectors.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 3 (+) — Chassis ground (–):
(B134) No. 4 (+) — Chassis ground (–):
(B134) No. 6 (+) — Chassis ground (–):
(B137) No. 1 (+) — Chassis ground (–):
(B137) No. 3 (+) — Chassis ground (–):
Is the voltage less than 1 V? Check the connec-
tor for poor contact
and check the har-
ness.
Replace the ECM if
no fault is found.
<Ref. to FU(STI)-
56, Engine Control
Module (ECM).>
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
ground circuit
Further tighten-
ing of the engine
ground terminal
Poor contact of
ECM connector
Poor contact of
coupling connector
15WRX_STI_US_EN.book 269 ージ 20  
EN(STI)(diag)-270
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DM:DTC P0616 STARTER RELAY CIRCUIT LOW
1. MODEL WITHOUT PUSH BUTTON START
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-155, DTC P0616 STARTER RELAY CIRCUIT LOW, Diag-
nostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, ENGINE
TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B72
7856
3412
22 8
B550
1
3
2
B225
5
B14
1
B106
1
M
7
B72
B136C:
B135B:
B14
1
B106
1
2
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29
3231
1234
56
2726
33 34 35
B136C:
B135B:
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
EN-10851
3
4
5
2
B26
C16
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-6
ECM
BATTERY
IGNITION SWITCH
F/B No. 21
MAIN SBF
CLUTCH START
SWITCH
STARTER MOTOR
STARTER
RELAY
FUSE HOLDER
15WRX_STI_US_EN.book 270 ージ 20  
EN(STI)(diag)-271
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2. MODEL WITH PUSH BUTTON START
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-155, DTC P0616 STARTER RELAY CIRCUIT LOW, Diag-
nostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check DTC using
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
STARTER RELAY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the starter relay.
3) Disconnect the connectors from ECM and
starter motor.
4) Measure the resistance of harness between
ECM connector and starter relay connector.
Connector & terminal
(B136) No. 16 — (B225) No. 1:
Is the resistance less than 1 Ω? Go to step 3.NOTE:
Check the follow-
ing item and repair
or replace if neces-
sary.
Open circuit of
harness between
ECM connector
and starter relay
connector
Blown out of fuse
3 CHECK HARNESS BETWEEN ECM AND
STARTER RELAY CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 16 — Chassis ground:
Is the resistance 1 MΩ or
more?
Repair the poor
contact of ECM
connector.
Repair the short
circuit to ground in
harness between
ECM connector
and starter relay
connector.
15WRX_STI_US_EN.book 271 ージ 20  
EN(STI)(diag)-272
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
B23
12345
6789
10
B550
228
B136C:
B135B:
B14
1
M
B574C:
B572A:
B28B23
3
21
A7
C6
1
B106
1
3
2
B225
5
28
30
29
B225
31
39 38
36 37
B225
19 20 21 22 23 24 25 26 27 28 29 30
789
10 11 12 13 14 15 16 17 18
123 456
B574C:
11 12
34
13 14
56
15 16
78
17 18
10
9
12
B572A:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29
3231
1234
56
2726
33 34 35
B136C:
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
B575
123
456789
10 11
12 13 14 15 16 17 18 19 20 21 22
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B106
1
2
EN-10852
B14
1
B550
1024
41
42
44
B225
40
2
B34
B26
C16
C27
B576B575
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-6
STARTER CUT
RELAY
FUSE
HOLDER
BATTERY
MAIN SBF
IG RELAY 1
(PUSH BUTTON
START)
F/B No. 26
STARTER RELAY
(PUSH BUTTON START)
STARTER
RELAY
CLUTCH START SWITCH
F/B No. 21
KEYLESS
ACCESS CM
STARTER MOTOR
FUSE
HOLDER
15WRX_STI_US_EN.book 272 ージ 20  
EN(STI)(diag)-273
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
STARTER RELAY CONNECTOR.
1) Turn the ignition to OFF.
2) Disconnect the connector from ECM.
3) Remove the starter relay.
4) Measure the resistance of harness between
ECM connector and starter relay connector.
Connector & terminal
(B136) No. 27 — (B225) No. 1:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and starter relay
connector
Blown out of fuse
2 CHECK HARNESS BETWEEN ECM AND
STARTER RELAY CONNECTOR.
1) Disconnect the connector from starter
motor.
2) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 27 — Chassis ground:
Is the resistance 1 MΩ or
more?
Repair the poor
contact of ECM
connector.
Repair the short
circuit to ground in
harness between
ECM connector
and starter relay
connector.
15WRX_STI_US_EN.book 273 ージ 20  
EN(STI)(diag)-274
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DN:DTC P0617 STARTER RELAY CIRCUIT HIGH
1. MODEL WITHOUT PUSH BUTTON START
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-156, DTC P0617 STARTER RELAY CIRCUIT HIGH, Diag-
nostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, ENGINE
TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B72
7856
3412
22 8
B550
1
3
2
B225
5
B14
1
B106
1
M
7
B72
B136C:
B135B:
B14
1
B106
1
2
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29
3231
1234
56
2726
33 34 35
B136C:
B135B:
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
EN-10851
3
4
5
2
B26
C16
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-6
ECM
BATTERY
IGNITION SWITCH
F/B No. 21
MAIN SBF
CLUTCH START
SWITCH
STARTER MOTOR
STARTER
RELAY
FUSE HOLDER
15WRX_STI_US_EN.book 274 ージ 20  
EN(STI)(diag)-275
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2. MODEL WITH PUSH BUTTON START
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-156, DTC P0617 STARTER RELAY CIRCUIT HIGH, Diag-
nostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
STARTER RELAY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 16 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and starter relay
connector.
Repair the poor
contact of ECM
connector.
15WRX_STI_US_EN.book 275 ージ 20  
EN(STI)(diag)-276
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
B23
12345
6789
10
B550
228
B136C:
B135B:
B14
1
M
B574C:
B572A:
B28B23
3
21
A7
C6
1
B106
1
3
2
B225
5
28
30
29
B225
31
39 38
36 37
B225
19 20 21 22 23 24 25 26 27 28 29 30
789
10 11 12 13 14 15 16 17 18
123 456
B574C:
11 12
34
13 14
56
15 16
78
17 18
10
9
12
B572A:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29
3231
1234
56
2726
33 34 35
B136C:
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
B575
123
456789
10 11
12 13 14 15 16 17 18 19 20 21 22
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B106
1
2
EN-10852
B14
1
B550
1024
41
42
44
B225
40
2
B34
B26
C16
C27
B576B575
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-6
STARTER CUT
RELAY
FUSE
HOLDER
BATTERY
MAIN SBF
IG RELAY 1
(PUSH BUTTON
START)
F/B No. 26
STARTER RELAY
(PUSH BUTTON START)
STARTER
RELAY
CLUTCH START SWITCH
F/B No. 21
KEYLESS
ACCESS CM
STARTER MOTOR
FUSE
HOLDER
15WRX_STI_US_EN.book 276 ージ 20  
EN(STI)(diag)-277
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK STARTER MOTOR.
1) Turn the ignition to ON.
2) Check the starter motor condition.
Is the starter motor rotating? Go to step 2. Repair the short
circuit to power
supply.
NOTE:
In this case, repair
the following har-
nesses:
Short circuit to
power supply in
harness between
ECM connector
and starter relay
connector
Short circuit to
power supply in
harness between
ECM connector
and starter motor
Short circuit to
power supply in
harness between
starter relay con-
nector and starter
motor
2 CHECK HARNESS BETWEEN STARTER
CUT RELAY CONNECTOR AND STARTER
RELAY CONNECTOR.
1) Turn the ignition to OFF.
2) Disconnect the connector from starter
motor.
3) Remove the starter cut relay and starter
relay.
4) Turn the ignition to ON.
5) Measure the voltage between starter relay
connector and chassis ground.
Connector & terminal
(B225) No. 2 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power
supply in harness
between starter cut
relay connector
and starter relay
connector.
Go to step 3.
3 CHECK STARTER CUT RELAY.
1) Connect the battery to starter cut relay ter-
minals No. 40 and No. 42.
2) Measure the resistance between starter cut
relay terminals.
Terminals
No. 41 — No. 44:
Is the resistance 1 MΩ or
more?
Go to step 6. Replace the starter
cut relay. <Ref. to
SL-116, Starter
Cut Relay.>
Go to step 4.
4 CHECK HARNESS BETWEEN ECM AND
STARTER RELAY CONNECTOR.
1) Disconnect the connector from ECM.
2) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 26 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
ECM connector
and starter relay
connector.
5 CHECK STARTER RELAY.
Measure the resistance between starter relay
terminals.
Terminals
No. 1 — No. 2:
Is the resistance 1 MΩ or
more?
Go to step 6. Replace the starter
relay. <Ref. to
EN(STI)(diag)-8,
LOCATION, Elec-
trical Component
Location.>
15WRX_STI_US_EN.book 277 ージ 20  
EN(STI)(diag)-278
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DO:DTC P062F INTERNAL CONTROL MODULE EEPROM ERROR
NOTE:
For the diagnostic procedure, refer to DTC P0606. <Ref. to EN(STI)(diag)-268, DTC P0606 CONTROL
MODULE PROCESSOR, Diagnostic Procedure with Diagnostic Trouble Code (DTC).>
6 CHECK HARNESS BETWEEN ECM, START-
ER RELAY CONNECTOR AND STARTER
MOTOR.
1) Disconnect the connector from ECM.
2) Turn the ignition to ON.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 27 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power
supply.
NOTE:
In this case, repair
the following har-
nesses:
Short circuit to
power supply in
harness between
ECM connector
and starter relay
connector
Short circuit to
power supply in
harness between
ECM connector
and starter motor
Short circuit to
power supply in
harness between
starter relay con-
nector and starter
motor
Repair the poor
contact of ECM
connector.
Step Check Yes No
15WRX_STI_US_EN.book 278 ージ 20  
EN(STI)(diag)-279
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DP:DTC P0685 ECM/PCM POWER RELAY CONTROL CIRCUIT/OPEN
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-159, DTC P0685 ECM/PCM POWER RELAY CONTROL
CIRCUIT/OPEN, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
34
40
WP
OP
WP
OP
B72
B550
216
B550
1024
B220
11
12
10
13
B134A:
B135B:
B136C:
B137D:
A3
A6
D1
D3
A4
36
35
E2
B21
C30
C2
B13
D7
C1
B220 B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
14
B225
36 37
EN-10853
WP
OP
B72
7856
3412
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SBF-6
ECM
: WITHOUT PUSH BUTTON START
: WITH PUSH BUTTON START
IG RELAY 1
(PUSH BUTTON
START)
BATTERY
MAIN
RELAY
FUSE
HOLDER
FUSE
HOLDER
M/B No. 13
F/B No. 12
IGNITION
SWITCH
MAIN SBF
15WRX_STI_US_EN.book 279 ージ 20  
EN(STI)(diag)-280
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK ECM CONNECTOR.
Check the connecting condition of ECM con-
nector.
Is the ECM connector correctly
connected?
Go to step 2. Connect the ECM
connector cor-
rectly.
2 CHECK HARNESS BETWEEN ECM AND
MAIN RELAY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the main relay.
3) Disconnect the connector from ECM.
4) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 13 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and main relay
connector.
3 CHECK HARNESS BETWEEN ECM AND
MAIN RELAY CONNECTOR.
1) Install the main relay.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 1 (+) — Chassis ground (–):
(B137) No. 7 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Short circuit to
power supply in
harness between
ECM connector
and main relay
connector
Defective main
relay
Repair the poor
contact of ECM
connector.
15WRX_STI_US_EN.book 280 ージ 20  
EN(STI)(diag)-281
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DQ:DTC P081A STARTER DISABLE CIRCUIT LOW
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-160, DTC P081A STARTER DISABLE CIRCUIT LOW, Di-
agnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Failure of engine to start
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 281 ージ 20  
EN(STI)(diag)-282
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
B23
12345
6789
10
B550
228
B136C:
B135B:
B14
1
M
B574C:
B572A:
B28B23
3
21
A7
C6
1
B106
1
3
2
B225
5
28
30
29
B225
31
39 38
36 37
B225
19 20 21 22 23 24 25 26 27 28 29 30
789
10 11 12 13 14 15 16 17 18
123 456
B574C:
11 12
34
13 14
56
15 16
78
17 18
10
9
12
B572A:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29
3231
1234
56
2726
33 34 35
B136C:
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
B575
123
456789
10 11
12 13 14 15 16 17 18 19 20 21 22
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B106
1
2
EN-10852
B14
1
B550
1024
41
42
44
B225
40
2
B34
B26
C16
C27
B576B575
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-6
STARTER CUT
RELAY
FUSE
HOLDER
BATTERY
MAIN SBF
IG RELAY 1
(PUSH BUTTON
START)
F/B No. 26
STARTER RELAY
(PUSH BUTTON START)
STARTER
RELAY
CLUTCH START SWITCH
F/B No. 21
KEYLESS
ACCESS CM
STARTER MOTOR
FUSE
HOLDER
15WRX_STI_US_EN.book 282 ージ 20  
EN(STI)(diag)-283
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN STARTER RE-
LAY (PUSH BUTTON START) CONNECTOR
AND STARTER CUT RELAY CONNECTOR.
1) Turn the ignition to OFF.
2) Remove the starter relay (push button start)
and starter cut relay.
3) Measure the resistance of harness between
starter relay (push button start) connector and
starter cut relay connector.
Connector & terminal
(B225) No. 28 — (B225) No. 42:
Is the resistance less than 1 Ω? Go to step 2. Repair the open
circuit in harness
between starter
relay (push button
start) connector
and starter cut
relay connector.
2 CHECK HARNESS BETWEEN ECM AND
STARTER CUT RELAY CONNECTOR.
1) Disconnect the connector from ECM.
2) Measure the resistance of harness between
ECM connector and starter cut relay connector.
Connector & terminal
(B135) No. 34 — (B225) No. 40:
Is the resistance less than 1 Ω? Go to step 3. Repair the open
circuit of harness
between ECM con-
nector and starter
cut relay connec-
tor.
3 CHECK STARTER CUT RELAY.
1) Connect the battery to starter cut relay ter-
minals No. 40 and No. 42.
2) Measure the resistance between starter cut
relay terminals.
Terminals
No. 41 — No. 44:
Is the resistance 1 MΩ or
more?
Repair the poor
contact of ECM
connector.
Replace the starter
cut relay. <Ref. to
SL-116, Starter
Cut Relay.>
15WRX_STI_US_EN.book 283 ージ 20  
EN(STI)(diag)-284
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DR:DTC P0851 NEUTRAL SWITCH INPUT CIRCUIT LOW (MT MODEL)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-161, DTC P0851 NEUTRAL SWITCH INPUT CIRCUIT LOW
(MT MODEL), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK INPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Place the shift lever in a position other than
neutral.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 35 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the poor
contact of ECM
connector.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
NEUTRAL POSITION SWITCH CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
neutral position switch.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 35 — Chassis ground:
Is the resistance 1 MΩ or
more?
Replace the neu-
tral position switch.
<Ref. to
6MT(TY85)-41,
Neutral Position
Switch.>
Repair the short
circuit to ground
harness between
ECM connector
and neutral posi-
tion switch connec-
tor.
EN-10872
123
456
B128
12
T12
T9B128
5
2
T2T12
2
1
B122
J/C
*
*
B122
34
56
12
78
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136
B136
35
4
ECM
*
: TERMINAL No. OPTIONAL ARRANGEMENT
NEUTRAL POSITION
SWITCH
15WRX_STI_US_EN.book 284 ージ 20  
EN(STI)(diag)-285
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DS:DTC P0852 NEUTRAL SWITCH INPUT CIRCUIT HIGH (MT MODEL)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-162, DTC P0852 NEUTRAL SWITCH INPUT CIRCUIT
HIGH (MT MODEL), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK INPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Place the shift lever in neutral.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 35 (+) — Chassis ground (–):
Is the voltage less than 1 V? Repair the poor
contact of ECM
connector.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
NEUTRAL POSITION SWITCH CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
neutral position switch.
3) Measure the resistance of harness between
ECM connector and transmission harness con-
nector.
Connector & terminal
(B136) No. 35 — (T12) No. 1:
(B136) No. 4 — (T12) No. 2:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and transmission
harness connector
Poor contact of
coupling connector
EN-10872
123
456
B128
12
T12
T9B128
5
2
T2T12
2
1
B122
J/C
*
*
B122
34
56
12
78
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136
B136
35
4
ECM
*
: TERMINAL No. OPTIONAL ARRANGEMENT
NEUTRAL POSITION
SWITCH
15WRX_STI_US_EN.book 285 ージ 20  
EN(STI)(diag)-286
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DT:DTC P1160 RETURN SPRING FAILURE
NOTE:
For the diagnostic procedure, refer to DTC P2101. <Ref. to EN(STI)(diag)-344, DTC P2101 THROTTLE AC-
TUATOR CONTROL MOTOR CIRCUIT RANGE/PERFORMANCE, Diagnostic Procedure with Diagnostic
Trouble Code (DTC).>
3 CHECK NEUTRAL POSITION SWITCH.
1) Place the shift lever in neutral.
2) Measure the resistance between transmis-
sion harness connector terminals.
Connector & terminal
(T2) No. 1 — (T2) No. 2:
Is the resistance less than 1 Ω? Repair the poor
contact of trans-
mission harness
connector.
Replace the neu-
tral position switch.
<Ref. to
6MT(TY85)-41,
Neutral Position
Switch.>
Step Check Yes No
15WRX_STI_US_EN.book 286 ージ 20  
EN(STI)(diag)-287
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DU:DTC P1410 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE
STUCK OPEN
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-164, DTC P1410 SECONDARY AIR INJECTION SYSTEM
SWITCHING VALVE STUCK OPEN, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK SECONDARY AIR COMBINATION
VALVE.
1) Remove the secondary air combination
valve. <Ref. to EC(STI)-54, Secondary Air
Combination Valve.>
2) Blow in air from the secondary air combina-
tion valve air inlet, and check whether there are
leaks at the pipe connections.
Are there air leaks from the pipe
connections?
Replace the sec-
ondary air combi-
nation valve on the
side with the air
leak. <Ref. to
EC(STI)-54, Sec-
ondary Air Combi-
nation Valve.>
Perform the diag-
nostic procedure of
DTC P2440. <Ref.
to EN(STI)(diag)-
413, DTC P2440
SECONDARY AIR
INJECTION SYS-
TEM SWITCHING
VALVE STUCK
OPEN (BANK1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
15WRX_STI_US_EN.book 287 ージ 20  
EN(STI)(diag)-288
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DV:DTC P1449 EVAPORATIVE EMISSION CONT. SYS. AIR FILTER CLOG
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-165, DTC P1449 EVAPORATIVE EMISSION CONT. SYS.
AIR FILTER CLOG, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK DRAIN TUBE A AND DRAIN PIPE
BETWEEN LEAK CHECK VALVE ASSEM-
BLY AND DRAIN FILTER.
Is the drain tube A or the drain
pipe between leak check valve
assembly and drain filter
clogged?
Replace the drain
tube A or the drain
pipe between leak
check valve
assembly and
drain filter. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.> <Ref.
to EC(STI)-26,
Drain Filter.>
Go to step 3.
3 CHECK DRAIN FILTER. Is the drain filter clogged? Replace the drain
filter. <Ref. to
EC(STI)-26, Drain
Filter.>
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
15WRX_STI_US_EN.book 288 ージ 20  
EN(STI)(diag)-289
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DW:DTC P1451 EVAPORATIVE EMISSION CONT. SYS.
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-166, DTC P1451 EVAPORATIVE EMISSION CONT. SYS.,
Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK DRAIN TUBE BETWEEN CANISTER
AND LEAK CHECK VALVE ASSEMBLY.
Is the drain tube between canis-
ter and leak check valve
assembly clogged?
Replace the drain
tube between the
canister and leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
Go to step 2.
2 CHECK HOSES BETWEEN CANISTER AND
FUEL TANK.
Are the hoses between the can-
ister and fuel tank clogged?
Replace the hoses
between the canis-
ter and fuel tank.
<Ref. to EC(STI)-
7, Canister.> <Ref.
to FU(STI)-67,
Fuel Tank.>
Replace the canis-
ter. <Ref. to
EC(STI)-7, Canis-
ter.>
After the operation
is complete, go to
the next step. Go to
step 3.
3 CHECK EVAPORATIVE EMISSION CON-
TROL SYSTEM.
Perform drive cycle I. <Ref. to EN(STI)(diag)-
56, DRIVE CYCLE I, PROCEDURE, Drive
Cycle.>
Is DTC P1451 displayed on the
display?
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
End.
15WRX_STI_US_EN.book 289 ージ 20  
EN(STI)(diag)-290
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DX:DTC P2004 INTAKE MANIFOLD RUNNER CONTROL STUCK OPEN (BANK 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-167, DTC P2004 INTAKE MANIFOLD RUNNER CONTROL
STUCK OPEN (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK TUMBLE GENERATOR VALVE RH.
1) Remove the tumble generator valve assem-
bly RH.
2) Check the tumble generator valve body.
Is there any dirt or clogging with
foreign objects in the tumble
generator valve?
Clean the tumble
generator valve.
Replace the tum-
ble generator valve
assembly RH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 290 ージ 20  
EN(STI)(diag)-291
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DY:DTC P2005 INTAKE MANIFOLD RUNNER CONTROL STUCK OPEN (BANK 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-168, DTC P2005 INTAKE MANIFOLD RUNNER CONTROL
STUCK OPEN (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK TUMBLE GENERATOR VALVE LH.
1) Remove the tumble generator valve assem-
bly LH.
2) Check the tumble generator valve body.
Is there any dirt or clogging with
foreign objects in the tumble
generator valve?
Clean the tumble
generator valve.
Replace the tum-
ble generator valve
assembly LH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 291 ージ 20  
EN(STI)(diag)-292
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
DZ:DTC P2006 INTAKE MANIFOLD RUNNER CONTROL STUCK CLOSED
(BANK 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-169, DTC P2006 INTAKE MANIFOLD RUNNER CONTROL
STUCK CLOSED (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK TUMBLE GENERATOR VALVE RH.
1) Remove the tumble generator valve assem-
bly RH.
2) Check the tumble generator valve body.
Is there any dirt or clogging with
foreign objects in the tumble
generator valve?
Clean the tumble
generator valve.
Replace the tum-
ble generator valve
assembly RH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 292 ージ 20  
EN(STI)(diag)-293
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EA:DTC P2007 INTAKE MANIFOLD RUNNER CONTROL STUCK CLOSED
(BANK 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-170, DTC P2007 INTAKE MANIFOLD RUNNER CONTROL
STUCK CLOSED (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK TUMBLE GENERATOR VALVE LH.
1) Remove the tumble generator valve assem-
bly LH.
2) Check the tumble generator valve body.
Is there any dirt or clogging with
foreign objects in the tumble
generator valve?
Clean the tumble
generator valve.
Replace the tum-
ble generator valve
assembly LH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 293 ージ 20  
EN(STI)(diag)-294
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EB:DTC P2008 INTAKE MANIFOLD RUNNER CONTROL CIRCUIT / OPEN
(BANK 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-171, DTC P2008 INTAKE MANIFOLD RUNNER CONTROL
CIRCUIT / OPEN (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
6
5A25
4A26
EN-10873
E51
E55
45
213
B134A:
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
29
30
27
28
E2B21
16
19
8
E55
1
2
D11
A29
3A19
E51
1
2
D10
3
4A24
5A23
ECM
TUMBLE GENERATOR
VALVE ASSY LH
TUMBLE GENERATOR
VALVE ASSY RH
15WRX_STI_US_EN.book 294 ージ 20  
EN(STI)(diag)-295
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
RH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from the ECM
and tumble generator valve assembly RH.
3) Measure the resistance of harness between
ECM connector and tumble generator valve
assembly RH connector.
Connector & terminal
(B134) No. 25 — (E55) No. 5:
(B134) No. 26 — (E55) No. 4:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly RH connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
RH CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 25 — Chassis ground:
(B134) No. 26 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly RH connector.
3 CHECK FOR POOR CONTACT.
Check for poor contact of tumble generator
valve assembly RH connector.
Is there poor contact of the tum-
ble generator valve assembly
RH connector?
Repair the poor
contact of tumble
generator valve
assembly RH con-
nector.
Replace the tum-
ble generator valve
assembly RH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 295 ージ 20  
EN(STI)(diag)-296
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EC:DTC P2009 INTAKE MANIFOLD RUNNER CONTROL CIRCUIT LOW (BANK 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-172, DTC P2009 INTAKE MANIFOLD RUNNER CONTROL
CIRCUIT LOW (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
6
5A25
4A26
EN-10873
E51
E55
45
213
B134A:
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
29
30
27
28
E2B21
16
19
8
E55
1
2
D11
A29
3A19
E51
1
2
D10
3
4A24
5A23
ECM
TUMBLE GENERATOR
VALVE ASSY LH
TUMBLE GENERATOR
VALVE ASSY RH
15WRX_STI_US_EN.book 296 ージ 20  
EN(STI)(diag)-297
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
RH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 25 (+) — Chassis ground (–):
(B134) No. 26 (+) — Chassis ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly RH connector.
Replace the tum-
ble generator valve
assembly RH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 297 ージ 20  
EN(STI)(diag)-298
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
ED:DTC P2011 INTAKE MANIFOLD RUNNER CONTROL CIRCUIT / OPEN
(BANK 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-173, DTC P2011 INTAKE MANIFOLD RUNNER CONTROL
CIRCUIT / OPEN (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
6
5A25
4A26
EN-10873
E51
E55
45
213
B134A:
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
29
30
27
28
E2B21
16
19
8
E55
1
2
D11
A29
3A19
E51
1
2
D10
3
4A24
5A23
ECM
TUMBLE GENERATOR
VALVE ASSY LH
TUMBLE GENERATOR
VALVE ASSY RH
15WRX_STI_US_EN.book 298 ージ 20  
EN(STI)(diag)-299
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
LH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
tumble generator valve assembly LH.
3) Measure the resistance of harness between
ECM connector and tumble generator valve
assembly LH connector.
Connector & terminal
(B134) No. 23 — (E51) No. 5:
(B134) No. 24 — (E51) No. 4:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly LH connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
LH CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 23 — Chassis ground:
(B134) No. 24 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly LH connector.
3 CHECK FOR POOR CONTACT.
Check for poor contact of tumble generator
valve assembly LH connector.
Is there poor contact of the tum-
ble generator valve assembly
LH connector?
Repair the poor
contact of tumble
generator valve
assembly LH con-
nector.
Replace the tum-
ble generator valve
assembly LH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 299 ージ 20  
EN(STI)(diag)-300
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EE:DTC P2012 INTAKE MANIFOLD RUNNER CONTROL CIRCUIT LOW (BANK 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-174, DTC P2012 INTAKE MANIFOLD RUNNER CONTROL
CIRCUIT LOW (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
6
5A25
4A26
EN-10873
E51
E55
45
213
B134A:
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
29
30
27
28
E2B21
16
19
8
E55
1
2
D11
A29
3A19
E51
1
2
D10
3
4A24
5A23
ECM
TUMBLE GENERATOR
VALVE ASSY LH
TUMBLE GENERATOR
VALVE ASSY RH
15WRX_STI_US_EN.book 300 ージ 20  
EN(STI)(diag)-301
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
LH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 23 (+) — Chassis ground (–):
(B134) No. 24 (+) — Chassis ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly LH connector.
Replace the tum-
ble generator valve
assembly LH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 301 ージ 20  
EN(STI)(diag)-302
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EF:DTC P2016 TUMBLE GENERATED VALVE POSITION SENSOR 1 CIRCUIT
LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-175, DTC P2016 TUMBLE GENERATED VALVE POSITION
SENSOR 1 CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Engine stalls.
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 302 ージ 20  
EN(STI)(diag)-303
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
6
5A25
4A26
EN-10873
E51
E55
45
213
B134A:
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
29
30
27
28
E2B21
16
19
8
E55
1
2
D11
A29
3A19
E51
1
2
D10
3
4A24
5A23
ECM
TUMBLE GENERATOR
VALVE ASSY LH
TUMBLE GENERATOR
VALVE ASSY RH
15WRX_STI_US_EN.book 303 ージ 20  
EN(STI)(diag)-304
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «TGV Position Sensor R»
using the Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «TGV Position
Sensor R» less than 0.2 V?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK POWER SUPPLY OF TUMBLE GEN-
ERATOR VALVE ASSEMBLY RH.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from tumble gen-
erator valve assembly RH.
3) Turn the ignition switch to ON.
4) Measure the voltage between tumble gener-
ator valve assembly RH connector and engine
ground.
Connector & terminal
(E55) No. 3 (+) — Engine ground (–):
Is the voltage 4.5 V or more? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly RH connector
Poor contact of
ECM connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
RH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness between
ECM connector and tumble generator valve
assembly RH connector.
Connector & terminal
(B137) No. 11 — (E55) No. 1:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly RH connector
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
RH CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 11 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly RH connector.
5 CHECK FOR POOR CONTACT.
Check for poor contact of ECM and tumble gen-
erator valve assembly RH connector.
Is there poor contact of ECM or
the tumble generator valve
assembly RH connector?
Repair the poor
contact of ECM or
tumble generator
valve assembly RH
connector.
Replace the tum-
ble generator valve
assembly RH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 304 ージ 20  
EN(STI)(diag)-305
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EG:DTC P2017 TUMBLE GENERATED VALVE POSITION SENSOR 1 CIRCUIT
HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-176, DTC P2017 TUMBLE GENERATED VALVE POSITION
SENSOR 1 CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Engine stalls.
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 305 ージ 20  
EN(STI)(diag)-306
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
6
5A25
4A26
EN-10873
E51
E55
45
213
B134A:
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
29
30
27
28
E2B21
16
19
8
E55
1
2
D11
A29
3A19
E51
1
2
D10
3
4A24
5A23
ECM
TUMBLE GENERATOR
VALVE ASSY LH
TUMBLE GENERATOR
VALVE ASSY RH
15WRX_STI_US_EN.book 306 ージ 20  
EN(STI)(diag)-307
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «TGV Position Sensor R»
using the Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «TGV Position
Sensor R» 5 V or more?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
RH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from tumble gen-
erator valve assembly RH.
3) Start the engine.
4) Read the value of «TGV Position Sensor R»
using the Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «TGV Position
Sensor R» 5 V or more?
Repair the short
circuit to power in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly RH connector.
Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
RH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness between
tumble generator valve assembly RH connector
and engine ground.
Connector & terminal
(E55) No. 2 — Engine ground:
Is the resistance less than 5 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly RH connector
Poor contact of
ECM connector
Poor contact of
coupling connector
4 CHECK FOR POOR CONTACT.
Check for poor contact of tumble generator
valve assembly RH connector.
Is there poor contact of the tum-
ble generator valve assembly
RH connector?
Repair the poor
contact of tumble
generator valve
assembly RH con-
nector.
Replace the tum-
ble generator valve
assembly RH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 307 ージ 20  
EN(STI)(diag)-308
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EH:DTC P2021 TUMBLE GENERATED VALVE POSITION SENSOR 2 CIRCUIT
LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-177, DTC P2021 TUMBLE GENERATED VALVE POSITION
SENSOR 2 CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Engine stalls.
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 308 ージ 20  
EN(STI)(diag)-309
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
6
5A25
4A26
EN-10873
E51
E55
45
213
B134A:
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
29
30
27
28
E2B21
16
19
8
E55
1
2
D11
A29
3A19
E51
1
2
D10
3
4A24
5A23
ECM
TUMBLE GENERATOR
VALVE ASSY LH
TUMBLE GENERATOR
VALVE ASSY RH
15WRX_STI_US_EN.book 309 ージ 20  
EN(STI)(diag)-310
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «TGV Position Sensor L»
using the Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «TGV Position
Sensor L» less than 0.2 V?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK POWER SUPPLY OF TUMBLE GEN-
ERATOR VALVE ASSEMBLY LH.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from tumble gen-
erator valve assembly LH.
3) Turn the ignition switch to ON.
4) Measure the voltage between tumble gener-
ator valve assembly LH connector and engine
ground.
Connector & terminal
(E51) No. 3 (+) — Engine ground (–):
Is the voltage 4.5 V or more? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly LH connector
Poor contact of
ECM connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
LH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness between
ECM connector and tumble generator valve
assembly LH connector.
Connector & terminal
(B137) No. 10 — (E51) No. 1:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly LH connector
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
LH CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 10 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly LH connector.
5 CHECK FOR POOR CONTACT.
Check for poor contact of ECM and tumble gen-
erator valve assembly LH connector.
Is there poor contact of ECM or
the tumble generator valve
assembly LH connector?
Repair the poor
contact of ECM or
tumble generator
valve assembly LH
connector.
Replace the tum-
ble generator valve
assembly LH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 310 ージ 20  
EN(STI)(diag)-311
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EI: DTC P2022 TUMBLE GENERATED VALVE POSITION SENSOR 2 CIRCUIT
HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-178, DTC P2022 TUMBLE GENERATED VALVE POSITION
SENSOR 2 CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Engine stalls.
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 311 ージ 20  
EN(STI)(diag)-312
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
6
5A25
4A26
EN-10873
E51
E55
45
213
B134A:
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
29
30
27
28
E2B21
16
19
8
E55
1
2
D11
A29
3A19
E51
1
2
D10
3
4A24
5A23
ECM
TUMBLE GENERATOR
VALVE ASSY LH
TUMBLE GENERATOR
VALVE ASSY RH
15WRX_STI_US_EN.book 312 ージ 20  
EN(STI)(diag)-313
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Start the engine.
2) Read the value of «TGV Position Sensor L»
using the Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «TGV Position
Sensor L» 5 V or more?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
LH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from tumble gen-
erator valve assembly LH.
3) Start the engine.
4) Read the value of «TGV Position Sensor L»
using the Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «TGV Position
Sensor L» 5 V or more?
Repair the short
circuit to power in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly LH connector.
Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND
TUMBLE GENERATOR VALVE ASSEMBLY
LH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of harness between
tumble generator valve assembly LH connector
and engine ground.
Connector & terminal
(E51) No. 2 — Engine ground:
Is the resistance less than 5 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and tumble gener-
ator valve assem-
bly LH connector
Poor contact of
ECM connector
Poor contact of
coupling connector
4 CHECK FOR POOR CONTACT.
Check for poor contact of tumble generator
valve assembly LH connector.
Is there poor contact of the tum-
ble generator valve assembly
LH connector?
Repair the poor
contact of tumble
generator valve
assembly LH con-
nector.
Replace the tum-
ble generator valve
assembly LH.
<Ref. to FU(STI)-
46, Tumble Gener-
ator Valve Assem-
bly.>
15WRX_STI_US_EN.book 313 ージ 20  
EN(STI)(diag)-314
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EJ:DTC P2088 INTAKE CAMSHAFT POSITION ACTUATOR CONTROL CIRCUIT
LOW (BANK 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-179, DTC P2088 INTAKE CAMSHAFT POSITION ACTUA-
TOR CONTROL CIRCUIT LOW (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
12
E38E37
18
2719 20 21 22
23
26
24
25
28 29 3332 3430 31
98
15
1413121110
17
16
1234567
B134
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
21
22
E2B21
E38
1
2
34
27
EN-10874
B134
32
33
1
2
17
16
E37
INTAKE OIL FLOW CONTROL
SOLENOID VALVE LH
INTAKE OIL FLOW CONTROL
SOLENOID VALVE RH
15WRX_STI_US_EN.book 314 ージ 20  
EN(STI)(diag)-315
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE RH
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
oil flow control solenoid valve RH.
3) Measure the resistance of harness between
ECM connector and oil flow control solenoid
valve RH connector.
Connector & terminal
(B134) No. 34 — (E38) No. 1:
(B134) No. 27 — (E38) No. 2:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and oil flow control
solenoid valve RH
connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE RH
CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 34 — Chassis ground:
(B134) No. 27 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and oil flow control
solenoid valve RH
connector.
3 CHECK OIL FLOW CONTROL SOLENOID
VALVE.
Measure the resistance between oil flow control
solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance 6 — 12 Ω? Repair the poor
contact of ECM
and oil flow control
solenoid valve RH
connector.
Replace the oil
flow control sole-
noid valve RH.
<Ref. to ME(STI)-
62, Camshaft.>
15WRX_STI_US_EN.book 315 ージ 20  
EN(STI)(diag)-316
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EK:DTC P2089 INTAKE CAMSHAFT POSITION ACTUATOR CONTROL CIRCUIT
HIGH (BANK 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-180, DTC P2089 INTAKE CAMSHAFT POSITION ACTUA-
TOR CONTROL CIRCUIT HIGH (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE RH
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
oil flow control solenoid valve RH.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 34 (+) — Chassis ground (–):
(B134) No. 27 (+) — Chassis ground (–):
Is the voltage less than 1 V? Go to step 2. Repair the short
circuit to power in
harness between
ECM connector
and oil flow control
solenoid valve RH
connector.
ECM
12
E38E37
18
2719 20 21 22
23
26
24
25
28 29 3332 3430 31
98
15
1413121110
17
16
1234567
B134
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
21
22
E2B21
E38
1
2
34
27
EN-10874
B134
32
33
1
2
17
16
E37
INTAKE OIL FLOW CONTROL
SOLENOID VALVE LH
INTAKE OIL FLOW CONTROL
SOLENOID VALVE RH
15WRX_STI_US_EN.book 316 ージ 20  
EN(STI)(diag)-317
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE RH
CONNECTOR.
Measure the resistance of harness between
ECM connector and oil flow control solenoid
valve RH connector.
Connector & terminal
(B134) No. 34 — (E38) No. 1:
(B134) No. 27 — (E38) No. 2:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and oil flow control
solenoid valve RH
connector
Poor contact of
coupling connector
3 CHECK OIL FLOW CONTROL SOLENOID
VALVE.
Measure the resistance between oil flow control
solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance 6 — 12 Ω? Repair the poor
contact of ECM
and oil flow control
solenoid valve RH
connector.
Replace the oil
flow control sole-
noid valve RH.
<Ref. to ME(STI)-
62, Camshaft.>
Step Check Yes No
15WRX_STI_US_EN.book 317 ージ 20  
EN(STI)(diag)-318
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EL:DTC P2090 EXHAUST CAMSHAFT POSITION ACTUATOR CONTROL CIR-
CUIT LOW (BANK 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-181, DTC P2090 EXHAUST CAMSHAFT POSITION ACTU-
ATOR CONTROL CIRCUIT LOW (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
12
E66E63
18
2719 20 21 22
23
26
24
25
28 29 3332 3430 31
98
15
1413121110
17
16
1234567
B134
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
7
17
E2B21
E63
1
2
7
15
EN-10875
B134
42
43
1
2
5
14
E66
ECM
EXHAUST OIL FLOW CONTROL
SOLENOID VALVE LH
EXHAUST OIL FLOW CONTROL
SOLENOID VALVE RH
15WRX_STI_US_EN.book 318 ージ 20  
EN(STI)(diag)-319
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE RH
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
oil flow control solenoid valve RH.
3) Measure the resistance of harness between
ECM connector and oil flow control solenoid
valve RH connector.
Connector & terminal
(B134) No. 7 — (E63) No. 1:
(B134) No. 15 — (E63) No. 2:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and oil flow control
solenoid valve RH
connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE RH
CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 7 — Chassis ground:
(B134) No. 15 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and oil flow control
solenoid valve RH
connector.
3 CHECK OIL FLOW CONTROL SOLENOID
VALVE.
Measure the resistance between oil flow control
solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance 6 — 12 Ω? Repair the poor
contact of ECM
and oil flow control
solenoid valve RH
connector.
Replace the oil
flow control sole-
noid valve RH.
<Ref. to FU(STI)-
48, Oil Flow Con-
trol Solenoid
Valve.>
15WRX_STI_US_EN.book 319 ージ 20  
EN(STI)(diag)-320
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EM:DTC P2091 EXHAUST CAMSHAFT POSITION ACTUATOR CONTROL CIR-
CUIT HIGH (BANK 1)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-182, DTC P2091 EXHAUST CAMSHAFT POSITION ACTU-
ATOR CONTROL CIRCUIT HIGH (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE RH
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
oil flow control solenoid valve RH.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 7 (+) — Chassis ground (–):
(B134) No. 15 (+) — Chassis ground (–):
Is the voltage less than 1 V? Go to step 2. Repair the short
circuit to power in
harness between
ECM connector
and oil flow control
solenoid valve RH
connector.
12
E66E63
18
2719 20 21 22
23
26
24
25
28 29 3332 3430 31
98
15
1413121110
17
16
1234567
B134
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
7
17
E2B21
E63
1
2
7
15
EN-10875
B134
42
43
1
2
5
14
E66
ECM
EXHAUST OIL FLOW CONTROL
SOLENOID VALVE LH
EXHAUST OIL FLOW CONTROL
SOLENOID VALVE RH
15WRX_STI_US_EN.book 320 ージ 20  
EN(STI)(diag)-321
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE RH
CONNECTOR.
Measure the resistance of harness between
ECM connector and oil flow control solenoid
valve RH connector.
Connector & terminal
(B134) No. 7 — (E63) No. 1:
(B134) No. 15 — (E63) No. 2:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and oil flow control
solenoid valve RH
connector
Poor contact of
coupling connector
3 CHECK OIL FLOW CONTROL SOLENOID
VALVE.
Measure the resistance between oil flow control
solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance 6 — 12 Ω? Repair the poor
contact of ECM
and oil flow control
solenoid valve RH
connector.
Replace the oil
flow control sole-
noid valve RH.
<Ref. to FU(STI)-
48, Oil Flow Con-
trol Solenoid
Valve.>
Step Check Yes No
15WRX_STI_US_EN.book 321 ージ 20  
EN(STI)(diag)-322
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EN:DTC P2092 INTAKE CAMSHAFT POSITION ACTUATOR CONTROL CIRCUIT
LOW (BANK 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-183, DTC P2092 INTAKE CAMSHAFT POSITION ACTUA-
TOR CONTROL CIRCUIT LOW (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
12
E38E37
18
2719 20 21 22
23
26
24
25
28 29 3332 3430 31
98
15
1413121110
17
16
1234567
B134
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
21
22
E2B21
E38
1
2
34
27
EN-10874
B134
32
33
1
2
17
16
E37
INTAKE OIL FLOW CONTROL
SOLENOID VALVE LH
INTAKE OIL FLOW CONTROL
SOLENOID VALVE RH
15WRX_STI_US_EN.book 322 ージ 20  
EN(STI)(diag)-323
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE LH
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
oil flow control solenoid valve LH.
3) Measure the resistance of harness between
ECM connector and oil flow control solenoid
valve LH connector.
Connector & terminal
(B134) No. 17 — (E37) No. 1:
(B134) No. 16 — (E37) No. 2:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and oil flow control
solenoid valve LH
connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE LH
CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 17 — Chassis ground:
(B134) No. 16 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and oil flow control
solenoid valve LH
connector.
3 CHECK OIL FLOW CONTROL SOLENOID
VALVE.
Measure the resistance between oil flow control
solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance 6 — 12 Ω? Repair the poor
contact of ECM
and oil flow control
solenoid valve LH
connector.
Replace the oil
flow control sole-
noid valve LH.
<Ref. to ME(STI)-
62, Camshaft.>
15WRX_STI_US_EN.book 323 ージ 20  
EN(STI)(diag)-324
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EO:DTC P2093 INTAKE CAMSHAFT POSITION ACTUATOR CONTROL CIRCUIT
HIGH (BANK 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-183, DTC P2093 INTAKE CAMSHAFT POSITION ACTUA-
TOR CONTROL CIRCUIT HIGH (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE LH
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
oil flow control solenoid valve LH.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 17 (+) — Chassis ground (–):
(B134) No. 16 (+) — Chassis ground (–):
Is the voltage less than 1 V? Go to step 2. Repair the short
circuit to power in
harness between
ECM connector
and oil flow control
solenoid valve LH
connector.
ECM
12
E38E37
18
2719 20 21 22
23
26
24
25
28 29 3332 3430 31
98
15
1413121110
17
16
1234567
B134
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
21
22
E2B21
E38
1
2
34
27
EN-10874
B134
32
33
1
2
17
16
E37
INTAKE OIL FLOW CONTROL
SOLENOID VALVE LH
INTAKE OIL FLOW CONTROL
SOLENOID VALVE RH
15WRX_STI_US_EN.book 324 ージ 20  
EN(STI)(diag)-325
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE LH
CONNECTOR.
Measure the resistance of harness between
ECM connector and oil flow control solenoid
valve LH connector.
Connector & terminal
(B134) No. 17 — (E37) No. 1:
(B134) No. 16 — (E37) No. 2:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and oil flow control
solenoid valve LH
connector
Poor contact of
coupling connector
3 CHECK OIL FLOW CONTROL SOLENOID
VALVE.
Measure the resistance between oil flow control
solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance 6 — 12 Ω? Repair the poor
contact of ECM
and oil flow control
solenoid valve LH
connector.
Replace the oil
flow control sole-
noid valve LH.
<Ref. to ME(STI)-
62, Camshaft.>
Step Check Yes No
15WRX_STI_US_EN.book 325 ージ 20  
EN(STI)(diag)-326
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EP:DTC P2094 EXHAUST CAMSHAFT POSITION ACTUATOR CONTROL CIR-
CUIT LOW (BANK 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-183, DTC P2094 EXHAUST CAMSHAFT POSITION ACTU-
ATOR CONTROL CIRCUIT LOW (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
12
E66E63
18
2719 20 21 22
23
26
24
25
28 29 3332 3430 31
98
15
1413121110
17
16
1234567
B134
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
7
17
E2B21
E63
1
2
7
15
EN-10875
B134
42
43
1
2
5
14
E66
ECM
EXHAUST OIL FLOW CONTROL
SOLENOID VALVE LH
EXHAUST OIL FLOW CONTROL
SOLENOID VALVE RH
15WRX_STI_US_EN.book 326 ージ 20  
EN(STI)(diag)-327
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE LH
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
oil flow control solenoid valve LH.
3) Measure the resistance of harness between
ECM connector and oil flow control solenoid
valve LH connector.
Connector & terminal
(B134) No. 5 — (E66) No. 1:
(B134) No. 14 — (E66) No. 2:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and oil flow control
solenoid valve LH
connector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE LH
CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 5 — Chassis ground:
(B134) No. 14 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and oil flow control
solenoid valve LH
connector.
3 CHECK OIL FLOW CONTROL SOLENOID
VALVE.
Measure the resistance between oil flow control
solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance 6 — 12 Ω? Repair the poor
contact of ECM
and oil flow control
solenoid valve LH
connector.
Replace the oil
flow control sole-
noid valve LH.
<Ref. to FU(STI)-
48, Oil Flow Con-
trol Solenoid
Valve.>
15WRX_STI_US_EN.book 327 ージ 20  
EN(STI)(diag)-328
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EQ:DTC P2095 EXHAUST CAMSHAFT POSITION ACTUATOR CONTROL CIR-
CUIT HIGH (BANK 2)
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-183, DTC P2095 EXHAUST CAMSHAFT POSITION ACTU-
ATOR CONTROL CIRCUIT HIGH (BANK 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE LH
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
oil flow control solenoid valve LH.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 5 (+) — Chassis ground (–):
(B134) No. 14 (+) — Chassis ground (–):
Is the voltage less than 1 V? Go to step 2. Repair the short
circuit to power in
harness between
ECM connector
and oil flow control
solenoid valve LH
connector.
12
E66E63
18
2719 20 21 22
23
26
24
25
28 29 3332 3430 31
98
15
1413121110
17
16
1234567
B134
15
16 17 18 19 20 21 22
23 24 25 26 27 28 29 30 31 32 33
13
14
11
12
9
10
78563412
34 35 36 37 38 39 40 41
42 43 44 45 46 47
48 49 50 51 52 53 54
B21
7
17
E2B21
E63
1
2
7
15
EN-10875
B134
42
43
1
2
5
14
E66
ECM
EXHAUST OIL FLOW CONTROL
SOLENOID VALVE LH
EXHAUST OIL FLOW CONTROL
SOLENOID VALVE RH
15WRX_STI_US_EN.book 328 ージ 20  
EN(STI)(diag)-329
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK HARNESS BETWEEN ECM AND OIL
FLOW CONTROL SOLENOID VALVE LH
CONNECTOR.
Measure the resistance of harness between
ECM connector and oil flow control solenoid
valve LH connector.
Connector & terminal
(B134) No. 5 — (E66) No. 1:
(B134) No. 14 — (E66) No. 2:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and oil flow control
solenoid valve LH
connector
Poor contact of
coupling connector
3 CHECK OIL FLOW CONTROL SOLENOID
VALVE.
Measure the resistance between oil flow control
solenoid valve terminals.
Terminals
No. 1 — No. 2:
Is the resistance 6 — 12 Ω? Repair the poor
contact of ECM
and oil flow control
solenoid valve LH
connector.
Replace the oil
flow control sole-
noid valve LH.
<Ref. to FU(STI)-
48, Oil Flow Con-
trol Solenoid
Valve.>
Step Check Yes No
15WRX_STI_US_EN.book 329 ージ 20  
EN(STI)(diag)-330
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
ER:DTC P2096 POST CATALYST FUEL TRIM SYSTEM TOO LEAN (BANK 1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-184, DTC P2096 POST CATALYST FUEL TRIM SYSTEM
TOO LEAN (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 330 ージ 20  
EN(STI)(diag)-331
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check DTC using
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 3.
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 331 ージ 20  
EN(STI)(diag)-332
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
3 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
3) Measure the resistance of harness between
ECM connector and front oxygen (A/F) sensor
connector.
Connector & terminal
(B136) No. 18 — (B379) No. 3:
(B136) No. 19 — (B379) No. 4:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and front oxygen
(A/F) sensor con-
nector
Poor contact of
front oxygen (A/F)
sensor connector
Poor contact of
ECM connector
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 18 — Chassis ground:
(B136) No. 19 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
ECM connector
and front oxygen
(A/F) sensor con-
nector.
5 CHECK OUTPUT SIGNAL FOR ECM.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between front oxygen
(A/F) sensor connector and chassis ground.
Connector & terminal
(B379) No. 4 (+) — Chassis ground (–):
Is the voltage 4.5 V or more? Go to step 7. Go to step 6.
6 CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/
F) sensor connector and chassis ground.
Connector & terminal
(B379) No. 3 (+) — Chassis ground (–):
Is the voltage 4.95 V or more? Go to step 7. Go to step 8.
7 CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/
F) sensor connector and chassis ground.
Connector & terminal
(B379) No. 3 (+) — Chassis ground (–):
(B379) No. 4 (+) — Chassis ground (–):
Is the voltage 8 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
After repair,
replace the ECM.
<Ref. to FU(STI)-
56, Engine Control
Module (ECM).>
Repair the poor
contact of ECM
connector.
8 CHECK EXHAUST SYSTEM. Are there holes or loose bolts
on exhaust system?
Repair the exhaust
system.
Go to step 9.
9 CHECK AIR INTAKE SYSTEM. Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
Go to step 10
.
Step Check Yes No
15WRX_STI_US_EN.book 332 ージ 20  
EN(STI)(diag)-333
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
10 CHECK FUEL PRESSURE.
WARNING:
Place “NO OPEN FLAMES” signs near the
working area.
CAUTION:
Be careful not to spill fuel.
1) Connect the front oxygen (A/F) sensor con-
nector.
2) Measure the fuel pressure while discon-
necting pressure regulator vacuum hose from
intake manifold. <Ref. to ME(STI)-25, INSPEC-
TION, Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze the
fuel return hose 2 to 3 times, then measure fuel
pressure again.
Is the measured value 284 —
314 kPa (2.9 — 3.2 kgf/cm
2
, 41
— 46 psi)?
Go to step 11. Check the fuel
pump and fuel
delivery line. <Ref.
to FU(STI)-83,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-99,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
11 CHECK FUEL PRESSURE.
After connecting the pressure regulator vacuum
hose, measure fuel pressure. <Ref. to ME(STI)-
25, INSPECTION, Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure fuel
pressure again.
If the measured value at this step is out of
specification, check or replace pressure regula-
tor and pressure regulator vacuum hose.
Is the measured value 230 —
260 kPa (2.4 — 2.7 kgf/cm
2
, 33
— 38 psi)?
Go to step 12. Check the fuel
pump and fuel
delivery line. <Ref.
to FU(STI)-83,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-99,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
12 CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm up completely.
2) Read the value of «Coolant Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Coolant Temp.»
75°C (167°F) or more?
Go to step 13. Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(STI)-33,
Engine Coolant
Temperature Sen-
sor.>
Step Check Yes No
15WRX_STI_US_EN.book 333 ージ 20  
EN(STI)(diag)-334
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
13 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Read the value of «Mass Air Flow» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Mass Air
Flow» 2.0 — 5.0 g/s (0.26 —
0.66 lb/m)?
Go to step 14. Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
14 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Open the front hood.
6) Measure the ambient temperature.
7) Read the value of «Intake Air Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Subtract ambient temperature
from «Intake Air Temp.». Is the
obtained value –10 — 50°C (–18
— 90°F)?
Go to step 15. Check the mass air
flow and intake air
temperature sen-
sor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
15 CHECK REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), and
keep the engine speed at 3,000 rpm. (2 minutes
maximum)
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Depress the clutch pedal.
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Rear O2 Sen-
sor» 0.490 V or more?
Go to step 16. Go to step 17.
Step Check Yes No
15WRX_STI_US_EN.book 334 ージ 20  
EN(STI)(diag)-335
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
16 CHECK REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), and
rapidly reduce the engine speed from 3,000
rpm.
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Depress the clutch pedal.
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Rear O2 Sen-
sor» 0.250 V or less?
Go to step 18. Go to step 17.
17 CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 19.
18 CHECK FRONT OXYGEN (A/F) SENSOR US-
ING REAR OXYGEN SENSOR SIGNAL.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), then
keep the engine idling for 5 minutes or more.
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value in «Rear O2 Sen-
sor» kept at 0.250 V or less for 5
minutes or more?
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
Go to step 19.
19 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM connector and rear oxygen sensor con-
nector.
Connector & terminal
(B136) No. 20 — (T6) No. 3:
(B135) No. 30 — (T6) No. 4:
Is the resistance less than 1 Ω? Go to step 20. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 335 ージ 20  
EN(STI)(diag)-336
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
20 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(T6) No. 3 (+) — Chassis ground (–):
Is the voltage 0.2 — 0.5 V? Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
ECM connector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 336 ージ 20  
EN(STI)(diag)-337
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
ES:DTC P2097 POST CATALYST FUEL TRIM SYSTEM TOO RICH (BANK 1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-185, DTC P2097 POST CATALYST FUEL TRIM SYSTEM
TOO RICH (BANK 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 337 ージ 20  
EN(STI)(diag)-338
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check DTC using
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 3.
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 338 ージ 20  
EN(STI)(diag)-339
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
3 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
3) Measure the resistance of harness between
ECM connector and front oxygen (A/F) sensor
connector.
Connector & terminal
(B136) No. 18 — (B379) No. 3:
(B136) No. 19 — (B379) No. 4:
Is the resistance less than 1 Ω? Go to step 4. Repair the open
circuit of harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
4 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 18 — Chassis ground:
(B136) No. 19 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
ECM connector
and front oxygen
(A/F) sensor con-
nector.
5 CHECK OUTPUT SIGNAL FOR ECM.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between front oxygen
(A/F) sensor connector and chassis ground.
Connector & terminal
(B379) No. 4 (+) — Chassis ground (–):
Is the voltage 4.5 V or more? Go to step 7. Go to step 6.
6 CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/
F) sensor connector and chassis ground.
Connector & terminal
(B379) No. 3 (+) — Chassis ground (–):
Is the voltage 4.95 V or more? Go to step 7. Go to step 8.
7 CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/
F) sensor connector and chassis ground.
Connector & terminal
(B379) No. 3 (+) — Chassis ground (–):
(B379) No. 4 (+) — Chassis ground (–):
Is the voltage 8 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
After repair,
replace the ECM.
<Ref. to FU(STI)-
56, Engine Control
Module (ECM).>
Repair the poor
contact of ECM
connector.
8 CHECK EXHAUST SYSTEM. Are there holes or loose bolts
on exhaust system?
Repair the exhaust
system.
Go to step 9.
9 CHECK AIR INTAKE SYSTEM. Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
Go to step 10.
Step Check Yes No
15WRX_STI_US_EN.book 339 ージ 20  
EN(STI)(diag)-340
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
10 CHECK FUEL PRESSURE.
WARNING:
Place “NO OPEN FLAMES” signs near the
working area.
CAUTION:
Be careful not to spill fuel.
1) Connect the front oxygen (A/F) sensor con-
nector.
2) Measure the fuel pressure while discon-
necting pressure regulator vacuum hose from
intake manifold. <Ref. to ME(STI)-25, INSPEC-
TION, Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze the
fuel return hose 2 to 3 times, then measure fuel
pressure again.
Is the measured value 284 —
314 kPa (2.9 — 3.2 kgf/cm
2
, 41
— 46 psi)?
Go to step 11. Check the fuel
pump and fuel
delivery line. <Ref.
to FU(STI)-83,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-99,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
11 CHECK FUEL PRESSURE.
After connecting the pressure regulator vacuum
hose, measure fuel pressure. <Ref. to ME(STI)-
25, INSPECTION, Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure fuel
pressure again.
If the measured value at this step is out of
specification, check or replace pressure regula-
tor and pressure regulator vacuum hose.
Is the measured value 230 —
260 kPa (2.4 — 2.7 kgf/cm
2
, 33
— 38 psi)?
Go to step 12. Check the fuel
pump and fuel
delivery line. <Ref.
to FU(STI)-83,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-99,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
12 CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm up completely.
2) Read the value of «Coolant Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Coolant Temp.»
75°C (167°F) or more?
Go to step 13. Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(STI)-33,
Engine Coolant
Temperature Sen-
sor.>
Step Check Yes No
15WRX_STI_US_EN.book 340 ージ 20  
EN(STI)(diag)-341
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
13 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Read the value of «Mass Air Flow» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Mass Air
Flow» 2.0 — 5.0 g/s (0.26 —
0.66 lb/m)?
Go to step 14. Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
14 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Open the front hood.
6) Measure the ambient temperature.
7) Read the value of «Intake Air Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Subtract ambient temperature
from «Intake Air Temp.». Is the
obtained value –10 — 50°C (–18
— 90°F)?
Go to step 15. Check the mass air
flow and intake air
temperature sen-
sor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
15 CHECK REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), and
keep the engine speed at 3,000 rpm. (2 minutes
maximum)
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Depress the clutch pedal.
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Rear O2 Sen-
sor» 0.490 V or more?
Go to step 16. Go to step 17.
Step Check Yes No
15WRX_STI_US_EN.book 341 ージ 20  
EN(STI)(diag)-342
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
16 CHECK REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), and
rapidly reduce the engine speed from 3,000
rpm.
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Depress the clutch pedal.
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Rear O2 Sen-
sor» 0.250 V or less?
Go to step 18. Go to step 17.
17 CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 19.
18 CHECK FRONT OXYGEN (A/F) SENSOR US-
ING REAR OXYGEN SENSOR SIGNAL.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), then
keep the engine idling for 5 minutes or more.
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value in «Rear O2 Sen-
sor» kept at 0.8 V or more for 5
minutes or more?
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
Go to step 19.
19 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM connector and rear oxygen sensor con-
nector.
Connector & terminal
(B136) No. 20 — (T6) No. 3:
(B135) No. 30 — (T6) No. 4:
Is the resistance less than 1 Ω? Go to step 20. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 342 ージ 20  
EN(STI)(diag)-343
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
20 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(T6) No. 3 (+) — Chassis ground (–):
Is the voltage 0.2 — 0.5 V? Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
ECM connector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 343 ージ 20  
EN(STI)(diag)-344
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
ET:DTC P2101 THROTTLE ACTUATOR CONTROL MOTOR CIRCUIT RANGE/
PERFORMANCE
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-186, DTC P2101 THROTTLE ACTUATOR CONTROL MO-
TOR CIRCUIT RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
Engine stalls.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 344 ージ 20  
EN(STI)(diag)-345
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Step Check Yes No
1 CHECK ELECTRONIC THROTTLE CON-
TROL RELAY.
1) Turn the ignition switch to OFF.
2) Remove the electronic throttle control relay.
3) Connect the battery to terminals No. 16 and
No. 17 of electronic throttle control relay.
4) Measure the resistance between electronic
throttle control relay terminals.
Terminals
No. 14 — No. 15:
Is the resistance less than 1 Ω? Go to step 2. Replace the elec-
tronic throttle con-
trol relay. <Ref. to
FU(STI)-60, Elec-
tronic Throttle
Control Relay.>
28
36
35
40
34
A3
A6
D1
D3
A4
B225
14
17
15
16
B122
J/C
*
*
B550
216
418
B220
1011
E2
B21
25
39
38
6
24
E57
B134A:
B135B:
B136C:
B137D:
A1
A2
A29
A28
6
5
4
3
2
1
A19
A18
C4
B17
B7
B225B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
321654
E57
B122
34
56
12
78
EN-10861
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
ECM
SBF-7
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
*
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
ELECTRONIC THROTTLE
CONTROL
MAIN
RELAY
FUSE
HOLDER
ELECTRONIC THROTTLE
CONTROL RELAY
15WRX_STI_US_EN.book 345 ージ 20  
EN(STI)(diag)-346
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
2 CHECK POWER SUPPLY OF ELECTRONIC
THROTTLE CONTROL RELAY.
Measure the voltage between electronic throttle
control relay connector and chassis ground.
Connector & terminal
(B225) No. 15 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 3. Repair the open or
ground short circuit
of power supply
circuit.
3 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY CONNECTOR.
1) Disconnect the connector from ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between electronic
throttle control relay connector and chassis
ground.
Connector & terminal
(B225) No. 17 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control relay con-
nector.
Go to step 4.
4 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between electronic
throttle control relay connector and chassis
ground.
Connector & terminal
(B225) No. 14 — Chassis ground:
(B225) No. 17 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
ECM connector
and electronic
throttle control
relay connector.
5 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY CONNECTOR.
Measure the resistance between ECM connec-
tor and electronic throttle control relay connec-
tor.
Connector & terminal
(B135) No. 7 — (B225) No. 14:
(B135) No. 17 — (B225) No. 17:
Is the resistance less than 1 Ω? Go to step 6. Repair the open
circuit in harness
between ECM con-
nector and elec-
tronic throttle
control relay con-
nector.
6 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from electronic
throttle control.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 19 — Chassis ground:
(B134) No. 18 — Chassis ground:
(B134) No. 18 — (B136) No. 4:
(B134) No. 28 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 7. Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
7 CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Connect the connector to ECM.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 6 — Engine ground:
(E57) No. 4 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 8. Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
Replace the ECM if
defective. <Ref. to
FU(STI)-56,
Engine Control
Module (ECM).>
Step Check Yes No
15WRX_STI_US_EN.book 346 ージ 20  
EN(STI)(diag)-347
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
8 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Disconnect the connector from ECM.
2) Measure the resistance of harness between
ECM connector and electronic throttle control
connector.
Connector & terminal
(B134) No. 18 — (E57) No. 6:
(B134) No. 28 — (E57) No. 4:
(B134) No. 29 — (E57) No. 3:
Is the resistance less than 1 Ω? Go to step 9. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and electronic
throttle control
connector
Poor contact of
coupling connector
9 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Connect the connector to ECM.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 3 — Engine ground:
Is the resistance less than 5 Ω? Go to step 10. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
ECM connector
Poor contact of
coupling connector
10 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 4 (+) — Engine ground (–):
(E57) No. 6 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
Go to step 11.
11 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B134) No. 19 — (B134) No. 18:
(B134) No. 19 — (B134) No. 28:
Is the resistance 1 MΩ or
more?
Go to step 12. Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
12 CHECK SENSOR OUTPUT.
1) Connect all connectors.
2) Start the engine and warm up completely.
3) Stop the engine, and then turn the ignition
switch to ON (engine OFF).
4) Read the value of «Main-Throttle Sensor»
using Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Main-Throttle
Sensor» 0.81 — 0.87 V?
Go to step 13. Repair the poor
contact of elec-
tronic throttle con-
trol connector.
Replace the elec-
tronic throttle con-
trol if defective.
<Ref. to FU(STI)-
15, Throttle Body.>
Step Check Yes No
15WRX_STI_US_EN.book 347 ージ 20  
EN(STI)(diag)-348
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
13 CHECK SENSOR OUTPUT.
Read the value of «Sub-Throttle Sensor» using
Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Sub-Throttle
Sensor» 1.64 — 1.70 V?
Go to step 14. Repair the poor
contact of elec-
tronic throttle con-
trol connector.
Replace the elec-
tronic throttle con-
trol if defective.
<Ref. to FU(STI)-
15, Throttle Body.>
14 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL MO-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
electronic throttle control.
3) Measure the resistance between ECM con-
nector and electronic throttle control connector.
Connector & terminal
(B134) No. 1 — (E57) No. 1:
(B134) No. 2 — (E57) No. 2:
Is the resistance less than 1 Ω? Go to step 15. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and electronic
throttle control
connector
Poor contact of
coupling connector
15 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL MO-
TOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 1 (+) — Engine ground (–):
(E57) No. 2 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
Go to step 16.
16 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL MO-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 1 — Engine ground:
(E57) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 17. Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
17 CHECK ELECTRONIC THROTTLE CON-
TROL MOTOR HARNESS.
Measure the resistance between electronic
throttle control connectors.
Connector & terminal
(E57) No. 1 — (E57) No. 2:
Is the resistance 1 MΩ or
more?
Go to step 18. Repair the short
circuit in harness
between ECM con-
nector and elec-
tronic throttle
control connector.
18 CHECK ELECTRONIC THROTTLE CON-
TROL GROUND CIRCUIT.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B134) No. 3 — Chassis ground:
(B134) No. 4 — Chassis ground:
(B134) No. 6 — Chassis ground:
(B137) No. 1 — Chassis ground:
(B137) No. 3 — Chassis ground:
Is the resistance less than 5 Ω? Go to step 19. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 348 ージ 20  
EN(STI)(diag)-349
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
19 CHECK ELECTRONIC THROTTLE CON-
TROL.
Measure the resistance between electronic
throttle control terminals.
Terminals
No. 1 — No. 2:
Is the resistance 50 Ω or less? Go to step 20. Replace the elec-
tronic throttle con-
trol. <Ref. to
FU(STI)-15, Throt-
tle Body.>
20 CHECK ELECTRONIC THROTTLE CON-
TROL.
Move the throttle valve to the fully open and fully
closed positions with fingers.
Check that the valve returns to the specified
position when releasing fingers.
Does the valve return to the
specified position? Standard
value: 3 mm (0.12 in) from fully
closed position
Repair the poor
contact of ECM
connector.
Replace the elec-
tronic throttle con-
trol. <Ref. to
FU(STI)-15, Throt-
tle Body.>
Step Check Yes No
15WRX_STI_US_EN.book 349 ージ 20  
EN(STI)(diag)-350
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EU:DTC P2102 THROTTLE ACTUATOR CONTROL MOTOR CIRCUIT LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-187, DTC P2102 THROTTLE ACTUATOR CONTROL MO-
TOR CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
Engine stalls.
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
28
36
35
40
34
A3
A6
D1
D3
A4
B225
14
17
15
16
B122
J/C
*
*
B550
216
418
B220
1011
E2
B21
25
39
38
6
24
E57
B134A:
B135B:
B136C:
B137D:
A1
A2
A29
A28
6
5
4
3
2
1
A19
A18
C4
B17
B7
B225B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
321654
E57
B122
34
56
12
78
EN-10861
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
ECM
SBF-7
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
*
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
ELECTRONIC THROTTLE
CONTROL
MAIN
RELAY
FUSE
HOLDER
ELECTRONIC THROTTLE
CONTROL RELAY
15WRX_STI_US_EN.book 350 ージ 20  
EN(STI)(diag)-351
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK ELECTRONIC THROTTLE CON-
TROL RELAY.
1) Turn the ignition switch to OFF.
2) Remove the electronic throttle control relay.
3) Connect the battery to terminals No. 16 and
No. 17 of electronic throttle control relay.
4) Measure the resistance between electronic
throttle control relay terminals.
Terminals
No. 14 — No. 15:
Is the resistance less than 1 Ω? Go to step 2. Replace the elec-
tronic throttle con-
trol relay. <Ref. to
FU(STI)-60, Elec-
tronic Throttle
Control Relay.>
2 CHECK POWER SUPPLY OF ELECTRONIC
THROTTLE CONTROL RELAY.
Measure the voltage between electronic throttle
control relay connector and chassis ground.
Connector & terminal
(B225) No. 15 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 3. Repair the open or
ground short circuit
of power supply
circuit.
3 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY CONNECTOR.
1) Disconnect the connector from ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between electronic
throttle control relay connector and chassis
ground.
Connector & terminal
(B225) No. 17 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control relay con-
nector.
Go to step 4.
4 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between electronic
throttle control relay connector and chassis
ground.
Connector & terminal
(B225) No. 14 — Chassis ground:
(B225) No. 17 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
ECM connector
and electronic
throttle control
relay connector.
5 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY CONNECTOR.
Measure the resistance between ECM connec-
tor and electronic throttle control relay connec-
tor.
Connector & terminal
(B135) No. 7 — (B225) No. 14:
(B135) No. 17 — (B225) No. 17:
Is the resistance less than 1 Ω? Repair the poor
contact of ECM
connector.
Repair the open
circuit in harness
between ECM con-
nector and elec-
tronic throttle
control relay con-
nector.
15WRX_STI_US_EN.book 351 ージ 20  
EN(STI)(diag)-352
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EV:DTC P2103 THROTTLE ACTUATOR CONTROL MOTOR CIRCUIT HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-188, DTC P2103 THROTTLE ACTUATOR CONTROL MO-
TOR CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
28
36
35
40
34
A3
A6
D1
D3
A4
B225
14
17
15
16
B122
J/C
*
*
B550
216
418
B220
1011
E2
B21
25
39
38
6
24
E57
B134A:
B135B:
B136C:
B137D:
A1
A2
A29
A28
6
5
4
3
2
1
A19
A18
C4
B17
B7
B225B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
321654
E57
B122
34
56
12
78
EN-10861
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
ECM
SBF-7
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
*
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
ELECTRONIC THROTTLE
CONTROL
MAIN
RELAY
FUSE
HOLDER
ELECTRONIC THROTTLE
CONTROL RELAY
15WRX_STI_US_EN.book 352 ージ 20  
EN(STI)(diag)-353
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EW:DTC P2109 THROTTLE/PEDAL POSITION SENSOR “A” MINIMUM STOP
PERFORMANCE
NOTE:
For the diagnostic procedure, refer to DTC P2101. <Ref. to EN(STI)(diag)-344, DTC P2101 THROTTLE AC-
TUATOR CONTROL MOTOR CIRCUIT RANGE/PERFORMANCE, Diagnostic Procedure with Diagnostic
Trouble Code (DTC).>
EX:DTC P2119 THROTTLE ACTUATOR CONTROL THROTTLE BODY RANGE/
PERFORMANCE
NOTE:
For the diagnostic procedure, refer to DTC P2101. <Ref. to EN(STI)(diag)-344, DTC P2101 THROTTLE AC-
TUATOR CONTROL MOTOR CIRCUIT RANGE/PERFORMANCE, Diagnostic Procedure with Diagnostic
Trouble Code (DTC).>
Step Check Yes No
1 CHECK ELECTRONIC THROTTLE CON-
TROL RELAY.
1) Turn the ignition switch to OFF.
2) Remove the electronic throttle control relay.
3) Measure the resistance between electronic
throttle control relay terminals.
Terminals
No. 14 — No. 15:
Is the resistance 1 MΩ or
more?
Go to step 2. Replace the elec-
tronic throttle con-
trol relay. <Ref. to
FU(STI)-60, Elec-
tronic Throttle
Control Relay.>
2 CHECK SHORT CIRCUIT OF ELECTRONIC
THROTTLE CONTROL RELAY POWER SUP-
PLY.
1) Turn the ignition switch to ON.
2) Measure the voltage between electronic
throttle control relay connector and chassis
ground.
Connector & terminal
(B225) No. 14 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control relay con-
nector.
Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL RE-
LAY CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 17 — Chassis ground:
Is the resistance 1 MΩ or
more?
Repair the poor
contact of ECM
connector.
Repair the short
circuit to ground in
harness between
ECM connector
and electronic
throttle control
relay connector.
15WRX_STI_US_EN.book 353 ージ 20  
EN(STI)(diag)-354
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EY:DTC P2122 THROTTLE/PEDAL POSITION SENSOR/SWITCH “D” CIRCUIT
LOW INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-193, DTC P2122 THROTTLE/PEDAL POSITION SENSOR/
SWITCH “D” CIRCUIT LOW INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
B83
456
123
*
*
B122
J/C
1
3
5
2
4
6
B134A:
B135B:
B136C:
B137D:
B122
34
56
12
78
56341
2
B315
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B315
C4
B23
B29
B21
B31
B30
B22
*
*
B83
J/C
EN-10876
ECM
*
: TERMINAL No. OPTIONAL ARRANGEMENT
ACCELERATOR PEDAL
POSITION SENSOR
15WRX_STI_US_EN.book 354 ージ 20  
EN(STI)(diag)-355
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
accelerator pedal position sensor.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 21 — Chassis ground:
(B135) No. 23 — Chassis ground:
(B135) No. 23 — (B136) No. 4:
Is the resistance 1 MΩ or
more?
Go to step 2. Repair the short
circuit to ground in
harness between
ECM connector
and accelerator
pedal position sen-
sor connector.
2 CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Connect the connector to ECM.
2) Measure the resistance between accelera-
tor pedal position sensor connector and chassis
ground.
Connector & terminal
(B315) No. 6 — Chassis ground:
Is the resistance 1 MΩ or
more?
Replace the accel-
erator pedal. <Ref.
to SP(STI)-4,
Accelerator
Pedal.>
Repair the short
circuit to ground in
harness between
ECM connector
and accelerator
pedal position sen-
sor connector.
Replace the ECM if
defective. <Ref. to
FU(STI)-56,
Engine Control
Module (ECM).>
15WRX_STI_US_EN.book 355 ージ 20  
EN(STI)(diag)-356
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
EZ:DTC P2123 THROTTLE/PEDAL POSITION SENSOR/SWITCH “D” CIRCUIT
HIGH INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-194, DTC P2123 THROTTLE/PEDAL POSITION SENSOR/
SWITCH “D” CIRCUIT HIGH INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
B83
456
123
*
*
B122
J/C
1
3
5
2
4
6
B134A:
B135B:
B136C:
B137D:
B122
34
56
12
78
56341
2
B315
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B315
C4
B23
B29
B21
B31
B30
B22
*
*
B83
J/C
EN-10876
ECM
*
: TERMINAL No. OPTIONAL ARRANGEMENT
ACCELERATOR PEDAL
POSITION SENSOR
15WRX_STI_US_EN.book 356 ージ 20  
EN(STI)(diag)-357
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
accelerator pedal position sensor.
3) Measure the resistance of harness between
ECM connector and accelerator pedal position
sensor connector.
Connector & terminal
(B135) No. 23 — (B315) No. 6:
(B135) No. 29 — (B315) No. 5:
Is the resistance less than 1 Ω? Go to step 2. Repair the open
circuit of harness
between ECM con-
nector and accel-
erator pedal
position sensor
connector.
2 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
1) Connect the connector to ECM.
2) Measure the resistance between accelera-
tor pedal position sensor connector and chassis
ground.
Connector & terminal
(B315) No. 5 — Chassis ground:
Is the resistance less than 5 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
ECM connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between accelerator
pedal position sensor connector and chassis
ground.
Connector & terminal
(B315) No. 6 (+) — Chassis ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power
supply in harness
between ECM con-
nector and accel-
erator pedal
position sensor
connector.
Go to step 4.
4 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B135) No. 21 — (B135) No. 23:
Is the resistance 1 MΩ or
more?
Repair the poor
contact of acceler-
ator pedal position
sensor connector.
Replace the accel-
erator pedal if
defective. <Ref. to
SP(STI)-4, Accel-
erator Pedal.>
Repair the short
circuit to power
supply in harness
between ECM con-
nector and accel-
erator pedal
position sensor
connector.
15WRX_STI_US_EN.book 357 ージ 20  
EN(STI)(diag)-358
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FA:DTC P2127 THROTTLE/PEDAL POSITION SENSOR/SWITCH “E” CIRCUIT
LOW INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-195, DTC P2127 THROTTLE/PEDAL POSITION SENSOR/
SWITCH “E” CIRCUIT LOW INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
B83
456
123
*
*
B122
J/C
1
3
5
2
4
6
B134A:
B135B:
B136C:
B137D:
B122
34
56
12
78
56341
2
B315
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B315
C4
B23
B29
B21
B31
B30
B22
*
*
B83
J/C
EN-10876
ECM
*
: TERMINAL No. OPTIONAL ARRANGEMENT
ACCELERATOR PEDAL
POSITION SENSOR
15WRX_STI_US_EN.book 358 ージ 20  
EN(STI)(diag)-359
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
accelerator pedal position sensor.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B135) No. 22 — Chassis ground:
(B135) No. 31 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 2. Repair the short
circuit to ground in
harness between
ECM connector
and accelerator
pedal position sen-
sor connector.
2 CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Connect the connector to ECM.
2) Measure the resistance between accelera-
tor pedal position sensor connector and chassis
ground.
Connector & terminal
(B315) No. 3 — Chassis ground:
Is the resistance 1 MΩ or
more?
Replace the accel-
erator pedal. <Ref.
to SP(STI)-4,
Accelerator
Pedal.>
Repair the short
circuit to ground in
harness between
ECM connector
and accelerator
pedal position sen-
sor connector.
Replace the ECM if
defective. <Ref. to
FU(STI)-56,
Engine Control
Module (ECM).>
15WRX_STI_US_EN.book 359 ージ 20  
EN(STI)(diag)-360
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FB:DTC P2128 THROTTLE/PEDAL POSITION SENSOR/SWITCH “E” CIRCUIT
HIGH INPUT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-196, DTC P2128 THROTTLE/PEDAL POSITION SENSOR/
SWITCH “E” CIRCUIT HIGH INPUT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
B83
456
123
*
*
B122
J/C
1
3
5
2
4
6
B134A:
B135B:
B136C:
B137D:
B122
34
56
12
78
56341
2
B315
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B315
C4
B23
B29
B21
B31
B30
B22
*
*
B83
J/C
EN-10876
ECM
*
: TERMINAL No. OPTIONAL ARRANGEMENT
ACCELERATOR PEDAL
POSITION SENSOR
15WRX_STI_US_EN.book 360 ージ 20  
EN(STI)(diag)-361
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
accelerator pedal position sensor.
3) Measure the resistance of harness between
ECM connector and accelerator pedal position
sensor connector.
Connector & terminal
(B135) No. 31 — (B315) No. 3:
(B135) No. 30 — (B315) No. 2:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and accelerator
pedal position sen-
sor connector
Poor contact of
joint connector
2 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
1) Connect the connector to ECM.
2) Measure the resistance between accelera-
tor pedal position sensor connector and chassis
ground.
Connector & terminal
(B315) No. 2 — Chassis ground:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
ECM connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between accelerator
pedal position sensor connector and chassis
ground.
Connector & terminal
(B315) No. 3 (+) — Chassis ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power
supply in harness
between ECM con-
nector and accel-
erator pedal
position sensor
connector.
Go to step 4.
4 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B135) No. 22 — (B135) No. 31:
Is the resistance 1 MΩ or
more?
Repair the poor
contact of acceler-
ator pedal position
sensor connector.
Replace the accel-
erator pedal if
defective. <Ref. to
SP(STI)-4, Accel-
erator Pedal.>
Repair the short
circuit to power
supply in harness
between ECM con-
nector and accel-
erator pedal
position sensor
connector.
15WRX_STI_US_EN.book 361 ージ 20  
EN(STI)(diag)-362
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FC:DTC P2135 THROTTLE/PEDAL POSITION SENSOR/SWITCH “A”/“B” VOLT-
AGE CORRELATION
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-197, DTC P2135 THROTTLE/PEDAL POSITION SENSOR/
SWITCH “A”/“B” VOLTAGE CORRELATION, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
28
36
35
40
34
A3
A6
D1
D3
A4
B225
14
17
15
16
B122
J/C
*
*
B550
216
418
B220
1011
E2
B21
25
39
38
6
24
E57
B134A:
B135B:
B136C:
B137D:
A1
A2
A29
A28
6
5
4
3
2
1
A19
A18
C4
B17
B7
B225B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
321654
E57
B122
34
56
12
78
EN-10861
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
ECM
SBF-7
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
*
BATTERY
: TERMINAL No. OPTIONAL ARRANGEMENT
ELECTRONIC THROTTLE
CONTROL
MAIN
RELAY
FUSE
HOLDER
ELECTRONIC THROTTLE
CONTROL RELAY
15WRX_STI_US_EN.book 362 ージ 20  
EN(STI)(diag)-363
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
electronic throttle control.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B134) No. 19 — Chassis ground:
(B134) No. 18 — Chassis ground:
(B134) No. 18 — (B136) No. 4:
(B134) No. 28 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 2. Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
2 CHECK SHORT CIRCUIT INSIDE THE ECM.
1) Connect the connector to ECM.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 4 — Engine ground:
(E57) No. 6 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the ground
short circuit of har-
ness between
ECM connector
and electronic
throttle control
connector.
Replace the ECM if
defective. <Ref. to
FU(STI)-56,
Engine Control
Module (ECM).>
3 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Disconnect the connector from ECM.
2) Measure the resistance of harness between
ECM connector and electronic throttle control
connector.
Connector & terminal
(B134) No. 18 — (E57) No. 6:
(B134) No. 28 — (E57) No. 4:
(B134) No. 29 — (E57) No. 3:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and electronic
throttle control
connector
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Connect the connector to ECM.
2) Measure the resistance between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 3 — Engine ground:
Is the resistance less than 5 Ω? Go to step 5. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
ECM connector
Poor contact of
coupling connector
5 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between electronic
throttle control connector and engine ground.
Connector & terminal
(E57) No. 4 (+) — Engine ground (–):
(E57) No. 6 (+) — Engine ground (–):
Is the voltage 5 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
Go to step 6.
15WRX_STI_US_EN.book 363 ージ 20  
EN(STI)(diag)-364
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
6 CHECK HARNESS BETWEEN ECM AND
ELECTRONIC THROTTLE CONTROL CON-
NECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nectors.
Connector & terminal
(B134) No. 19 — (B134) No. 18:
(B134) No. 19 — (B134) No. 28:
Is the resistance 1 MΩ or
more?
Repair the poor
contact of elec-
tronic throttle con-
trol connector.
Replace the elec-
tronic throttle con-
trol if defective.
<Ref. to FU(STI)-
15, Throttle Body.>
Repair the short
circuit to power in
the harness
between ECM con-
nector and elec-
tronic throttle
control connector.
Step Check Yes No
15WRX_STI_US_EN.book 364 ージ 20  
EN(STI)(diag)-365
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FD:DTC P2138 THROTTLE/PEDAL POSITION SENSOR/SWITCH “D”/“E” VOLT-
AGE CORRELATION
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-199, DTC P2138 THROTTLE/PEDAL POSITION SENSOR/
SWITCH “D”/“E” VOLTAGE CORRELATION, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
Poor driving performance
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
B83
456
123
*
*
B122
J/C
1
3
5
2
4
6
B134A:
B135B:
B136C:
B137D:
B122
34
56
12
78
56341
2
B315
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B315
C4
B23
B29
B21
B31
B30
B22
*
*
B83
J/C
EN-10876
ECM
*
: TERMINAL No. OPTIONAL ARRANGEMENT
ACCELERATOR PEDAL
POSITION SENSOR
15WRX_STI_US_EN.book 365 ージ 20  
EN(STI)(diag)-366
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK ACCELERATOR PEDAL POSITION
SENSOR OUTPUT.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
Main accelerator pedal position sensor
signal
(B135) No. 23 (+) — Chassis ground (–):
Sub accelerator pedal position sensor
signal
(B135) No. 31 (+) — Chassis ground (–):
Is the difference in measured
values for the main accelerator
pedal position sensor signal
and the sub accelerator pedal
position sensor signal 0 V?
Go to step 3. Go to step 2.
2 CHECK ACCELERATOR PEDAL POSITION
SENSOR OUTPUT.
1) Measure the voltage between accelerator
pedal position sensor connector and chassis
ground.
Connector & terminal
(B315) No. 6 (+) — Chassis ground (–):
(B315) No. 3 (+) — Chassis ground (–):
Is the difference in measured
values for the main accelerator
pedal position sensor signal
and the sub accelerator pedal
position sensor signal 0 V?
Replace the accel-
erator pedal. <Ref.
to SP(STI)-4,
Accelerator
Pedal.>
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and accelerator
pedal position sen-
sor connector
Short circuit to
ground in harness
between ECM con-
nector and accel-
erator pedal
position sensor
connector
3 CHECK HARNESS BETWEEN ECM AND AC-
CELERATOR PEDAL POSITION SENSOR
CONNECTOR.
Measure the resistance of harness between
accelerator pedal position sensor connector
and chassis ground.
Connector & terminal
(B315) No. 5 — Chassis ground:
(B315) No. 2 — Chassis ground:
Is the resistance less than 5 Ω? Repair the poor
contact of ECM
connector.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit of
harness between
ECM connector
and accelerator
pedal position sen-
sor connector
Open circuit of
harness between
ECM connector
and engine ground
Poor contact of
ECM connector
Poor contact of
coupling connector
15WRX_STI_US_EN.book 366 ージ 20  
EN(STI)(diag)-367
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FE:DTC P2158 VEHICLE SPEED SENSOR "B"
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-201, DTC P2158 VEHICLE SPEED SENSOR "B", Diagnos-
tic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK DTC OF VDC.
Check DTC of VDC.
Is DTC of VDC displayed? Perform the diag-
nosis according to
DTC. <Ref. to
VDC(diag)-42, List
of Diagnostic Trou-
ble Code (DTC).>
Repair the poor
contact of ECM
connector.
15WRX_STI_US_EN.book 367 ージ 20  
EN(STI)(diag)-368
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FF:DTC P2195 O2 SENSOR SIGNAL BIASED/STUCK LEAN (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-202, DTC P2195 O2 SENSOR SIGNAL BIASED/STUCK
LEAN (BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 368 ージ 20  
EN(STI)(diag)-369
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
3) Measure the resistance of harness between
ECM connector and front oxygen (A/F) sensor
connector.
Connector & terminal
(B136) No. 18 — (B379) No. 3:
(B136) No. 19 — (B379) No. 4:
Is the resistance less than 1 Ω? Go to step 3. Repair the open
circuit of harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
3 CHECK FOR POOR CONTACT.
Check for poor contact of the front oxygen (A/F)
sensor connector.
Is there poor contact of front
oxygen (A/F) sensor connec-
tor?
Repair the poor
contact of front
oxygen (A/F) sen-
sor connector.
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
15WRX_STI_US_EN.book 369 ージ 20  
EN(STI)(diag)-370
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FG:DTC P2196 O2 SENSOR SIGNAL BIASED/STUCK RICH (BANK 1 SENSOR 1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-204, DTC P2196 O2 SENSOR SIGNAL BIASED/STUCK
RICH (BANK 1 SENSOR 1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 370 ージ 20  
EN(STI)(diag)-371
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance between ECM con-
nector and chassis ground.
Connector & terminal
(B136) No. 18 — Chassis ground:
(B136) No. 19 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and front oxygen
(A/F) sensor con-
nector.
3 CHECK OUTPUT SIGNAL FOR ECM.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 19 (+) — Chassis ground (–):
Is the voltage 4.5 V or more? Go to step 5. Go to step 4.
4 CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 18 (+) — Chassis ground (–):
Is the voltage 4.95 V or more? Go to step 5. Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
5 CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between ECM connector
and chassis ground.
Connector & terminal
(B136) No. 18 (+) — Chassis ground (–):
(B136) No. 19 (+) — Chassis ground (–):
Is the voltage 8 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
After repair,
replace the ECM.
<Ref. to FU(STI)-
56, Engine Control
Module (ECM).>
Repair the poor
contact of ECM
connector.
15WRX_STI_US_EN.book 371 ージ 20  
EN(STI)(diag)-372
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FH:DTC P219A BANK 1 AIR-FUEL RATIO IMBALANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-206, DTC P219A BANK 1 AIR-FUEL RATIO IMBALANCE,
Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Engine stalls.
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
B1
456
123
B379
21
43
*
B1
J/C
B379
1
B550
519
22
B225
21
2
3
4
B134A:
B136C:
B137D:
C9
C19
C18
C6
C5
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10857
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
SBF-5
ECM
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
FRONT OXYGEN (A/F)
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 372 ージ 20  
EN(STI)(diag)-373
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 373 ージ 20  
EN(STI)(diag)-374
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK FRONT OXYGEN (A/F) SENSOR
CONNECTOR AND COUPLING CONNEC-
TOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connectors from ECM and
front oxygen (A/F) sensor.
3) Measure the resistance of harness between
ECM connector and front oxygen (A/F) sensor
connector.
Connector & terminal
(B136) No. 18 — (B379) No. 3:
(B136) No. 19 — (B379) No. 4:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and front oxygen
(A/F) sensor con-
nector
Poor contact of
coupling connector
10
B220
11
B550
216
51
52
53
54
E2
B21
48
2
1
E5
B134
10
11
12
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
B134
8
5
6
10 11 12 13 14 15
72134
16
30
19 20 22
28 29
9
17
18 2521 23 24
3231
26 27
33 34
EN-10855
2
1
E16
2
1
E6
2
1
E17
13
E5
E6
E16
E17
21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
ECM
FUEL INJECTOR No. 4
FUEL INJECTOR No. 3
FUEL INJECTOR No. 2
FUEL INJECTOR No. 1
BATTERY
FUSE HOLDER
MAIN RELAY
15WRX_STI_US_EN.book 374 ージ 20  
EN(STI)(diag)-375
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
3 CHECK HARNESS BETWEEN ECM AND
FRONT OXYGEN (A/F) SENSOR CONNEC-
TOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 18 — Chassis ground:
(B136) No. 19 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 4. Repair the short
circuit to ground in
harness between
ECM connector
and front oxygen
(A/F) sensor con-
nector.
4 CHECK OUTPUT SIGNAL FOR ECM.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between front oxygen
(A/F) sensor connector and chassis ground.
Connector & terminal
(B379) No. 4 (+) — Chassis ground (–):
Is the voltage 4.5 V or more? Go to step 6. Go to step 5.
5 CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/
F) sensor connector and chassis ground.
Connector & terminal
(B379) No. 3 (+) — Chassis ground (–):
Is the voltage 4.95 V or more? Go to step 6. Go to step 7.
6 CHECK OUTPUT SIGNAL FOR ECM.
Measure the voltage between front oxygen (A/
F) sensor connector and chassis ground.
Connector & terminal
(B379) No. 3 (+) — Chassis ground (–):
(B379) No. 4 (+) — Chassis ground (–):
Is the voltage 8 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and front
oxygen (A/F) sen-
sor connector.
After repair,
replace the ECM.
<Ref. to FU(STI)-
56, Engine Control
Module (ECM).>
Repair the poor
contact of ECM
connector.
7 CHECK EXHAUST SYSTEM. Are there holes or loose bolts
on exhaust system?
Repair the exhaust
system.
Go to step 8.
8 CHECK AIR INTAKE SYSTEM. Are there holes, loose bolts or
disconnection of hose on air
intake system?
Repair the air
intake system.
Go to step 9.
9 CHECK FUEL PRESSURE.
WARNING:
Place “NO OPEN FLAMES” signs near the
working area.
CAUTION:
Be careful not to spill fuel.
1) Connect the front oxygen (A/F) sensor con-
nector.
2) Measure the fuel pressure while discon-
necting pressure regulator vacuum hose from
intake manifold. <Ref. to ME(STI)-25, INSPEC-
TION, Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze the
fuel return hose 2 to 3 times, then measure fuel
pressure again.
Is the measured value 284 —
314 kPa (2.9 — 3.2 kg/cm
2
, 41
— 46 psi)?
Go to step 10. Check the fuel
pump and fuel
delivery line. <Ref.
to FU(STI)-83,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-99,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
Step Check Yes No
15WRX_STI_US_EN.book 375 ージ 20  
EN(STI)(diag)-376
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
10 CHECK FUEL PRESSURE.
After connecting the pressure regulator vacuum
hose, measure fuel pressure. <Ref. to ME(STI)-
25, INSPECTION, Fuel Pressure.>
CAUTION:
Release fuel pressure before removing the
fuel pressure gauge.
NOTE:
If fuel pressure does not increase, squeeze
fuel return hose 2 to 3 times, then measure fuel
pressure again.
If the measured value at this step is out of
specification, check or replace pressure regula-
tor vacuum hose.
Is the measured value 230 —
260 kPa (2.4 — 2.7 kg/cm
2
, 33
— 38 psi)?
Go to step 11. Check the fuel
pump and fuel
delivery line. <Ref.
to FU(STI)-83,
INSPECTION,
Fuel Pump.> <Ref.
to FU(STI)-99,
INSPECTION,
Fuel Delivery,
Return and Evapo-
ration Lines.>
11 CHECK ENGINE COOLANT TEMPERATURE
SENSOR.
1) Start the engine and warm up completely.
2) Read the value of «Coolant Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Coolant Temp.»
75°C (167°F) or more?
Go to step 12. Replace the
engine coolant
temperature sen-
sor. <Ref. to
FU(STI)-33,
Engine Coolant
Temperature Sen-
sor.>
12 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Read the value of «Mass Air Flow» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Mass Air
Flow» 2.0 — 5.0 g/s (0.26 —
0.66 lb/m)?
Go to step 13. Replace the mass
air flow and intake
air temperature
sensor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
Step Check Yes No
15WRX_STI_US_EN.book 376 ージ 20  
EN(STI)(diag)-377
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
13 CHECK MASS AIR FLOW AND INTAKE AIR
TEMPERATURE SENSOR.
1) Start the engine and warm up engine until
coolant temperature is higher than 75°C
(167°F).
2) Place the shift lever in neutral position.
3) Turn the A/C switch to OFF.
4) Turn all the accessory switches to OFF.
5) Open the front hood.
6) Measure the ambient temperature.
7) Read the value of «Intake Air Temp.» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Subtract ambient temperature
from «Intake Air Temp.». Is the
obtained value –10 — 50°C (–18
— 90°F)?
Go to step 14. Check the mass air
flow and intake air
temperature sen-
sor. <Ref. to
FU(STI)-40, Mass
Air Flow and Intake
Air Temperature
Sensor.>
14 CHECK REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), and
keep the engine speed at 3,000 rpm. (2 minutes
maximum)
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Depress the clutch pedal.
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Rear O2 Sen-
sor» 0.490 V or more?
Go to step 15. Go to step 16.
15 CHECK REAR OXYGEN SENSOR DATA.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), and
rapidly reduce the engine speed from 3,000
rpm.
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Depress the clutch pedal.
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value of «Rear O2 Sen-
sor» 0.250 V or less?
Go to step 17. Go to step 16.
16 CHECK REAR OXYGEN SENSOR CONNEC-
TOR AND COUPLING CONNECTOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 18.
Step Check Yes No
15WRX_STI_US_EN.book 377 ージ 20  
EN(STI)(diag)-378
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
17 CHECK FRONT OXYGEN (A/F) SENSOR US-
ING REAR OXYGEN SENSOR SIGNAL.
1) Warm up the engine until engine coolant
temperature is higher than 75°C (167°F), then
keep the engine idling for 5 minutes or more.
2) Read the value of «Rear O2 Sensor» using
the Subaru Select Monitor or a general scan
tool.
NOTE:
Subaru Select Monitor
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
General scan tool
For detailed operation procedures, refer to the
general scan tool operation manual.
Is the value in «Rear O2 Sen-
sor» kept at 0.250 V or less for 5
minutes or more?
Replace the front
oxygen (A/F) sen-
sor. <Ref. to
FU(STI)-52, Front
Oxygen (A/F) Sen-
sor.>
Go to step 18.
18 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM connector and rear oxygen sensor con-
nector.
Connector & terminal
(B136) No. 20 — (T6) No. 3:
(B135) No. 30 — (T6) No. 4:
Is the resistance less than 1 Ω? Go to step 19. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
coupling connector
19 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(T6) No. 3 (+) — Chassis ground (–):
Is the voltage 0.2 — 0.5 V? Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
Go to step 20.
20 CHECK OUTPUT SIGNAL OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground on faulty cylinders.
Connector & terminal
#1 (B134) No. 10 (+) — Chassis ground (–):
#2 (B134) No. 11 (+) — Chassis ground (–):
#3 (B134) No. 12 (+) — Chassis ground (–):
#4 (B134) No. 13 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 25. Go to step 21.
21 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector
on faulty cylinders.
3) Measure the resistance between fuel injec-
tor connector and engine ground on faulty cylin-
ders.
Connector & terminal
#1 (E5) No. 2 — Engine ground:
#2 (E16) No. 2 — Engine ground:
#3 (E6) No. 2 — Engine ground:
#4 (E17) No. 2 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 22. Repair the short
circuit to ground in
harness between
ECM connector
and fuel injector
connector.
Step Check Yes No
15WRX_STI_US_EN.book 378 ージ 20  
EN(STI)(diag)-379
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
22 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
Measure the resistance of harness between
ECM connector and fuel injector connector on
faulty cylinders.
Connector & terminal
#1 (B134) No. 10 — (E5) No. 2:
#2 (B134) No. 11 — (E16) No. 2:
#3 (B134) No. 12 — (E6) No. 2:
#4 (B134) No. 13 — (E17) No. 2:
Is the resistance less than 1 Ω? Go to step 23. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and fuel injector
connector
Poor contact of
coupling connector
23 CHECK FUEL INJECTOR.
Measure the resistance between fuel injector
terminals on faulty cylinder.
Terminals
No. 1 — No. 2:
Is the resistance 5 — 20 Ω? Go to step 24. Replace the faulty
fuel injector. <Ref.
to FU(STI)-43,
Fuel Injector.>
24 CHECK POWER SUPPLY LINE.
1) Turn the ignition switch to ON.
2) Measure the voltage between fuel injector
connector of faulty cylinders and engine
ground.
Connector & terminal
#1 (E5) No. 1 (+) — Engine ground (–):
#2 (E16) No. 1 (+) — Engine ground (–):
#3 (E6) No. 1 (+) — Engine ground (–):
#4 (E17) No. 1 (+) — Engine ground (–):
Is the voltage 10 V or more? Repair the poor
contact of all con-
nectors in fuel
injector circuit.
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
the main relay and
fuel injector con-
nector on faulty
cylinders
Poor contact of
coupling connector
Poor contact of
main relay connec-
tor
25 CHECK HARNESS BETWEEN ECM AND
FUEL INJECTOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from fuel injector
on faulty cylinders.
3) Turn the ignition switch to ON.
4) Measure the voltage between ECM connec-
tor and chassis ground on faulty cylinders.
Connector & terminal
#1 (B134) No. 10 (+) — Chassis ground (–):
#2 (B134) No. 11 (+) — Chassis ground (–):
#3 (B134) No. 12 (+) — Chassis ground (–):
#4 (B134) No. 13 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and fuel injector
connectors.
Go to step 26.
26 CHECK FUEL INJECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance between fuel injec-
tor terminals on faulty cylinder.
Terminals
No. 1 — No. 2:
Is the resistance 5 — 20 Ω? Go to step 27. Replace the faulty
fuel injector. <Ref.
to FU(STI)-43,
Fuel Injector.>
Step Check Yes No
15WRX_STI_US_EN.book 379 ージ 20  
EN(STI)(diag)-380
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
27 CHECK INSTALLATION CONDITION OF
CAMSHAFT POSITION SENSOR/CRANK-
SHAFT POSITION SENSOR.
Is the camshaft position sensor
or crankshaft position sensor
loosely installed?
Tighten the cam-
shaft position sen-
sor or crankshaft
position sensor.
<Ref. to FU(STI)-
35, Camshaft Posi-
tion Sensor.> <Ref.
to FU(STI)-34,
Crankshaft Posi-
tion Sensor.>
Go to step 28.
28 CHECK CRANK SPROCKET.
Remove the timing belt cover. <Ref. to ME(STI)-
50, REMOVAL, Timing Belt Cover.>
Is the crank sprocket rusted or
does it have broken teeth?
Replace the crank
sprocket. <Ref. to
ME(STI)-61, Crank
Sprocket.>
Go to step 29.
29 CHECK INSTALLATION CONDITION OF
TIMING BELT.
Turn the crankshaft using ST, and align the
alignment mark on crank sprocket with align-
ment mark on cylinder block.
ST 499987500 CRANKSHAFT
SOCKET
Is the timing belt dislocated
from its proper position?
Repair the installa-
tion condition of
timing belt. <Ref. to
ME(STI)-51, Tim-
ing Belt.>
Go to step 30.
30 CHECK FUEL LEVEL. Is the fuel meter indication
higher than the “Lower” level?
Go to step 31. Refill the fuel so
that the fuel meter
indication is higher
than the “Lower”
level, and proceed
to the next step. Go
to step 31.
31 CHECK STATUS OF MALFUNCTION INDI-
CATOR LIGHT.
1) Clear the memory using the Subaru Select
Monitor or general scan tool. <Ref. to
EN(STI)(diag)-59, Clear Memory Mode.>
2) Start the engine, and drive the vehicle 10
minutes or more.
Does the malfunction indicator
light illuminate or blink?
Go to step 33. Go to step 32.
32 CHECK CAUSE OF MISFIRE. Was the cause of misfire identi-
fied when the engine is run-
ning?
Finish diagnostics
operation, if the
engine has no
abnormality.
Repair the poor
contact of connec-
tor.
NOTE:
In this case, repair
the following item:
Poor contact of
ignition coil con-
nector
Poor contact of
fuel injector con-
nector on faulty
cylinders
Poor contact of
ECM connector
Poor contact of
coupling connector
Step Check Yes No
15WRX_STI_US_EN.book 380 ージ 20  
EN(STI)(diag)-381
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
33 CHECK AIR INTAKE SYSTEM. Is there any fault in air intake
system?
Repair the air
intake system.
NOTE:
Check the follow-
ing items.
Are there air
leaks or air suction
caused by loose or
dislocated nuts
and bolts?
Are there cracks
or any disconnec-
tion of hoses?
Go to step 34.
34 CHECK MISFIRE SYMPTOM.
1) Turn the ignition switch to ON.
2) Check for DTC. <Ref. to EN(STI)(diag)-42,
Read Diagnostic Trouble Code (DTC).>
Does the Subaru Select Moni-
tor or general scan tool indicate
only one DTC?
Go to step 37. Go to step 35.
35 CHECK DTC. Is DTC P0301 and P0303 dis-
played on the Subaru Select
Monitor or general scan tool?
Go to step 38. Go to step 36.
36 CHECK DTC. Is DTC P0302 and P0304 dis-
played on the Subaru Select
Monitor or general scan tool?
Go to step 39. Go to step 40.
37 ONLY ONE CYLINDER. Is there any fault in the cylin-
der?
Repair or replace
faulty parts.
NOTE:
Check the follow-
ing items.
Spark plug
Ignition coil
Fuel injector
Compression ra-
tio
Go to DTC P0171.
<Ref. to
EN(STI)(diag)-
158, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
38 GROUP OF #1 AND #3 CYLINDERS. Are there any faults in #1 and
#3 cylinders?
Repair or replace
faulty parts.
NOTE:
Check the follow-
ing items.
Spark plug
Ignition coil
Fuel injector
Compression ra-
tio
Skipping timing
belt teeth
Go to DTC P0171.
<Ref. to
EN(STI)(diag)-
158, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
39 GROUP OF #2 AND #4 CYLINDERS. Are there any faults in #2 and
#4 cylinders?
Repair or replace
faulty parts.
NOTE:
Check the follow-
ing items.
Spark plug
Ignition coil
Fuel injector
Compression ra-
tio
Skipping timing
belt teeth
Go to DTC P0171.
<Ref. to
EN(STI)(diag)-
158, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
Step Check Yes No
15WRX_STI_US_EN.book 381 ージ 20  
EN(STI)(diag)-382
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
40 CYLINDER AT RANDOM. Is the engine idle rough? Go to DTC P0171.
<Ref. to
EN(STI)(diag)-
158, DTC P0171
SYSTEM TOO
LEAN (BANK 1),
Diagnostic Proce-
dure with Diagnos-
tic Trouble Code
(DTC).>
Repair or replace
faulty parts.
NOTE:
Check the follow-
ing items.
Spark plug
Ignition coil
Fuel injector
Compression ra-
tio
Step Check Yes No
15WRX_STI_US_EN.book 382 ージ 20  
EN(STI)(diag)-383
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FI: DTC P2257 AIR SYSTEM CONTROL "A" CIRCUIT LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-211, DTC P2257 AIR SYSTEM CONTROL "A" CIRCUIT
LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 383 ージ 20  
EN(STI)(diag)-384
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
A:
M/B
F37
B: B143
E40
B143B:
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
F37A:
1234
56789
10 11 12 13 14 15 16 17 18 19 20
12
F11
5
11
15
1
2
9
10
34 7
12 13
8
6
16
14
F9
12
E41
123
456
E40
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
F9
A13
28
1
6
47
E2
B21
46
B550
216
B220
11
10
1
2
3
6
4
1
2
2
60A
10A
14
12
11
13
15
16
6
5
7
10
8
9
4
1
3
2
B10
B20
A5B2
A17B13
A20
A18B12
B4 A8
A19
D9
A29
B27
B20
B8
B137D:
B135B:
B134A:
A16
B14
1
E41 F11
EN-10867
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SECONDARY
AIR PUMP
SECONDARY
AIR COMBINATION
VALVE RH
SECONDARY
AIR PUMP RELAY
SECONDARY
AIR COMBINATION
VALVE RELAY 2
SECONDARY
AIR COMBINATION
VALVE RELAY 1
MAIN SBF
MAIN RELAY
BATTERY
FUSE HOLDER
RELAY HOLDER
SECONDARY AIR
COMBINATION VALVE LH
(WITH BUILT-IN
PRESSURE SENSOR)
15WRX_STI_US_EN.book 384 ージ 20  
EN(STI)(diag)-385
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR PUMP RELAY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Remove the secondary air pump relay.
4) Measure the resistance of harness between
ECM connector and secondary air pump relay
connector.
Connector & terminal
(B135) No. 27 — (F9) No. 13:
Is the resistance less than 1 Ω? Go to step 2. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and secondary air
pump relay con-
nector
Poor contact of
coupling connector
2 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR PUMP RELAY CONNEC-
TOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B135) No. 27 — Chassis ground:
Is the resistance 1 MΩ or
more?
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
Repair the short
circuit to ground in
harness between
ECM connector
and secondary air
pump relay con-
nector.
15WRX_STI_US_EN.book 385 ージ 20  
EN(STI)(diag)-386
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FJ:DTC P2258 AIR SYSTEM CONTROL "A" CIRCUIT HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-212, DTC P2258 AIR SYSTEM CONTROL "A" CIRCUIT
HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 386 ージ 20  
EN(STI)(diag)-387
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
A:
M/B
F37
B: B143
E40
B143B:
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
F37A:
1234
56789
10 11 12 13 14 15 16 17 18 19 20
12
F11
5
11
15
1
2
9
10
34 7
12 13
8
6
16
14
F9
12
E41
123
456
E40
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
F9
A13
28
1
6
47
E2
B21
46
B550
216
B220
11
10
1
2
3
6
4
1
2
2
60A
10A
14
12
11
13
15
16
6
5
7
10
8
9
4
1
3
2
B10
B20
A5B2
A17B13
A20
A18B12
B4 A8
A19
D9
A29
B27
B20
B8
B137D:
B135B:
B134A:
A16
B14
1
E41 F11
EN-10867
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SECONDARY
AIR PUMP
SECONDARY
AIR COMBINATION
VALVE RH
SECONDARY
AIR PUMP RELAY
SECONDARY
AIR COMBINATION
VALVE RELAY 2
SECONDARY
AIR COMBINATION
VALVE RELAY 1
MAIN SBF
MAIN RELAY
BATTERY
FUSE HOLDER
RELAY HOLDER
SECONDARY AIR
COMBINATION VALVE LH
(WITH BUILT-IN
PRESSURE SENSOR)
15WRX_STI_US_EN.book 387 ージ 20  
EN(STI)(diag)-388
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR PUMP RELAY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Remove the secondary air pump relay.
4) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B135) No. 27 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and secondary air
pump relay con-
nector.
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
15WRX_STI_US_EN.book 388 ージ 20  
EN(STI)(diag)-389
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FK:DTC P2270 O2 SENSOR SIGNAL BIASED/STUCK LEAN (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-213, DTC P2270 O2 SENSOR SIGNAL BIASED/STUCK
LEAN (BANK 1 SENSOR 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 389 ージ 20  
EN(STI)(diag)-390
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK REAR OXYGEN SENSOR CONNEC-
TOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM connector and rear oxygen sensor con-
nector.
Connector & terminal
(B136) No. 20 — (T6) No. 3:
(B135) No. 30 — (T6) No. 4:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Connect the connector to ECM.
2) Turn the ignition switch to ON.
3) Measure the voltage between rear oxygen
sensor connector and chassis ground.
Connector & terminal
(T6) No. 3 (+) — Chassis ground (–):
Is the voltage 0.15 V or more? Repair the short
circuit to power in
the harness
between ECM con-
nector and rear
oxygen sensor
connector.
Go to step 4.
4 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following items.
Looseness and improper fitting of exhaust
system parts
Damage (crack, hole etc.) of parts
Damage (crack, hole etc.) between front oxy-
gen (A/F) sensor and rear oxygen sensor
Is there any fault in exhaust
system?
Repair or replace
faulty parts.
Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
15WRX_STI_US_EN.book 390 ージ 20  
EN(STI)(diag)-391
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FL:DTC P2271 O2 SENSOR SIGNAL BIASED/STUCK RICH (BANK 1 SENSOR 2)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-215, DTC P2271 O2 SENSOR SIGNAL BIASED/STUCK
RICH (BANK 1 SENSOR 2), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
21
43
T6
B83B1
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
T6
2
B550
519
22
B225
21
4
3
1
2
T5B19
1
3
4
B134A:
B135B:
B136C:
B137D:
C9
B30
C20
B6
B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
EN-10858
36
35
E2
B21
A4
D3
D1
A6
A3
40
34
*
B1
J/C
*
*
B83
J/C
*
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
B19
12
34
*
SBF-5
ECM
A/F, OXYGEN
SENSOR RELAY
BATTERY
FUSE HOLDER
REAR OXYGEN
SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 391 ージ 20  
EN(STI)(diag)-392
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK REAR OXYGEN SENSOR CONNEC-
TOR.
Has water entered the connec-
tor?
Completely
remove any water
inside.
Go to step 2.
2 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
rear oxygen sensor.
3) Measure the resistance of harness between
ECM connector and rear oxygen sensor con-
nector.
Connector & terminal
(B136) No. 20 — (T6) No. 3:
(B135) No. 30 — (T6) No. 4:
Is the resistance less than 1 Ω? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and rear oxygen
sensor connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
REAR OXYGEN SENSOR CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B136) No. 20 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 4. Repair the short
circuit to ground in
harness between
ECM connector
and rear oxygen
sensor connector.
4 CHECK EXHAUST SYSTEM.
Check exhaust system parts.
NOTE:
Check the following items.
Looseness and improper fitting of exhaust
system parts
Damage (crack, hole etc.) of parts
Damage (crack, hole etc.) between front oxy-
gen (A/F) sensor and rear oxygen sensor
Is there any fault in exhaust
system?
Repair or replace
faulty parts.
Replace the rear
oxygen sensor.
<Ref. to FU(STI)-
54, Rear Oxygen
Sensor.>
15WRX_STI_US_EN.book 392 ージ 20  
EN(STI)(diag)-393
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FM:DTC P2401 EVAPORATIVE EMISSION SYSTEM LEAK DETECTION PUMP
CONTROL CIRCUIT LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-216, DTC P2401 EVAPORATIVE EMISSION SYSTEM
LEAK DETECTION PUMP CONTROL CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
B97
B83
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
B135B:
B136C:
B137D:
EN-10868
20
15
16
18
R1B97
19
17
*
*
B83
J/C
*
3
4
R400
1234
5678
R400
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
D27
5
1
6
7
8
B30
B4
B22
C21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
VACUUM PUMP
MAIN RELAY
BATTERY
FUSE HOLDER
LEAK CHECK VALVE ASSY
SWITCHING VALVE
PRESSURE SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 393 ージ 20  
EN(STI)(diag)-394
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 27 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 2. Go to step 3.
2 CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.
Is there poor contact of ECM
connector?
Repair the poor
contact of ECM
connector.
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary open or
short circuit of har-
ness or temporary
poor contact of
connector may be
the cause.
3 CHECK POWER SUPPLY TO LEAK CHECK
VALVE ASSEMBLY.
Measure the voltage between the leak check
valve assembly connector and engine ground.
Connector & terminal
(R400) No. 3 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 4. Repair the power
supply circuit.
4 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
the leak check valve assembly.
3) Measure the resistance between leak check
valve assembly and chassis ground.
Connector & terminal
(R400) No. 4 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
ECM connector
and leak check
valve assembly
connector.
5 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
Measure the resistance of harness between
ECM connector and the leak check valve
assembly connector.
Connector & terminal
(B137) No. 27 — (R400) No. 4:
Is the resistance less than 1 Ω? Go to step 6. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and the leak check
valve assembly
connector
Poor contact of
coupling connector
15WRX_STI_US_EN.book 394 ージ 20  
EN(STI)(diag)-395
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
6 CHECK LEAK CHECK VALVE ASSEMBLY.
Check the vacuum pump of the leak check valve
assembly. <Ref. to EC(STI)-47, CHECK VAC-
UUM PUMP, INSPECTION, Leak Check Valve
Assembly.>
Is the vacuum pump of the leak
check valve assembly OK?
Repair the poor
contact in the leak
check valve
assembly connec-
tor.
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
Step Check Yes No
15WRX_STI_US_EN.book 395 ージ 20  
EN(STI)(diag)-396
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FN:DTC P2402 EVAPORATIVE EMISSION SYSTEM LEAK DETECTION PUMP
CONTROL CIRCUIT HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-217, DTC P2402 EVAPORATIVE EMISSION SYSTEM
LEAK DETECTION PUMP CONTROL CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
B97
B83
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
B135B:
B136C:
B137D:
EN-10868
20
15
16
18
R1B97
19
17
*
*
B83
J/C
*
3
4
R400
1234
5678
R400
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
D27
5
1
6
7
8
B30
B4
B22
C21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
VACUUM PUMP
MAIN RELAY
BATTERY
FUSE HOLDER
LEAK CHECK VALVE ASSY
SWITCHING VALVE
PRESSURE SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 396 ージ 20  
EN(STI)(diag)-397
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the leak
check valve assembly.
3) Turn the ignition switch to ON.
4) Measure the voltage between leak check
valve assembly and chassis ground.
Connector & terminal
(R400) No. 4 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and leak check
valve assembly
connector.
Go to step 2.
2 CHECK LEAK CHECK VALVE ASSEMBLY.
1) Turn the ignition switch to OFF.
2) Check the vacuum pump of the leak check
valve assembly. <Ref. to EC(STI)-47, CHECK
VACUUM PUMP, INSPECTION, Leak Check
Valve Assembly.>
Is the vacuum pump of the leak
check valve assembly OK?
Repair the poor
contact in the leak
check valve
assembly connec-
tor.
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
15WRX_STI_US_EN.book 397 ージ 20  
EN(STI)(diag)-398
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FO:DTC P2404 EVAPORATIVE EMISSION SYSTEM LEAK DETECTION PUMP
SENSE CIRCUIT RANGE/PERFORMANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-218, DTC P2404 EVAPORATIVE EMISSION SYSTEM
LEAK DETECTION PUMP SENSE CIRCUIT RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC)
Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
B97
B83
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
B135B:
B136C:
B137D:
EN-10868
20
15
16
18
R1B97
19
17
*
*
B83
J/C
*
3
4
R400
1234
5678
R400
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
D27
5
1
6
7
8
B30
B4
B22
C21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
VACUUM PUMP
MAIN RELAY
BATTERY
FUSE HOLDER
LEAK CHECK VALVE ASSY
SWITCHING VALVE
PRESSURE SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 398 ージ 20  
EN(STI)(diag)-399
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK ELCM PUMP.
Operate the ELCM pump using the Subaru
Select Monitor.
NOTE:
For detailed procedures, refer to “System Oper-
ation Check Mode”. <Ref. to EN(STI)(diag)-60,
System Operation Check Mode.>
Does the ELCM pump operate? Go to step 6. Go to step 3.
3 CHECK POWER SUPPLY OF LEAK CHECK
VALVE ASSEMBLY.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the leak
check valve assembly.
3) Turn the ignition switch to ON.
4) Measure the voltage between the leak
check valve assembly connector and chassis
ground.
Connector & terminal
(R400) No. 3 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
the main relay and
the leak check
valve assembly
connector
Poor contact of
main relay connec-
tor
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness between
ECM connector and the leak check valve
assembly connector.
Connector & terminal
(B137) No. 27 — (R400) No. 4:
Is the resistance less than 1 Ω? Go to step 5. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and the leak check
valve assembly
connector
Poor contact of
coupling connector
5 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B137) No. 27 — Chassis ground:
Is the resistance 1 MΩ or
more?
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
Repair the short
circuit to ground in
harness between
ECM connector
and leak check
valve assembly
connector.
15WRX_STI_US_EN.book 399 ージ 20  
EN(STI)(diag)-400
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
6 CHECK ELCM SWITCHING VALVE.
Operate the ELCM switching valve using the
Subaru Select Monitor.
NOTE:
For detailed procedures, refer to “System Oper-
ation Check Mode”. <Ref. to EN(STI)(diag)-60,
System Operation Check Mode.>
Does the ELCM switching valve
operate?
Go to step 10. Go to step 7.
7 CHECK POWER SUPPLY OF LEAK CHECK
VALVE ASSEMBLY.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the leak
check valve assembly.
3) Turn the ignition switch to ON.
4) Measure the voltage between the leak
check valve assembly connector and chassis
ground.
Connector & terminal
(R400) No. 5 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 8. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
the main relay and
the leak check
valve assembly
connector
Poor contact of
main relay connec-
tor
Poor contact of
coupling connector
8 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness between
ECM connector and the leak check valve
assembly connector.
Connector & terminal
(B135) No. 4 — (R400) No. 1:
Is the resistance less than 1 Ω? Go to step 9. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and the leak check
valve assembly
connector
Poor contact of
coupling connector
9 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Measure the resistance of harness between
ECM connector and chassis ground.
Connector & terminal
(B135) No. 4 — Chassis ground:
Is the resistance 1 MΩ or
more?
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
Repair the short
circuit to ground in
harness between
ECM connector
and leak check
valve assembly
connector.
10 CHECK EVAPORATIVE EMISSION CON-
TROL SYSTEM.
Perform drive cycle I. <Ref. to EN(STI)(diag)-
56, DRIVE CYCLE I, PROCEDURE, Drive
Cycle.>
Is DTC P2404 displayed on the
display?
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
Step Check Yes No
15WRX_STI_US_EN.book 400 ージ 20  
EN(STI)(diag)-401
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FP:DTC P2419 EVAPORATIVE EMISSION SYSTEM SWITCHING VALVE CON-
TROL CIRCUIT LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-219, DTC P2419 EVAPORATIVE EMISSION SYSTEM
SWITCHING VALVE CONTROL CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
B97
B83
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
B135B:
B136C:
B137D:
EN-10868
20
15
16
18
R1B97
19
17
*
*
B83
J/C
*
3
4
R400
1234
5678
R400
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
D27
5
1
6
7
8
B30
B4
B22
C21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
VACUUM PUMP
MAIN RELAY
BATTERY
FUSE HOLDER
LEAK CHECK VALVE ASSY
SWITCHING VALVE
PRESSURE SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 401 ージ 20  
EN(STI)(diag)-402
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground.
Connector & terminal
(B135) No. 4 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 2. Go to step 3.
2 CHECK FOR POOR CONTACT.
Check for poor contact of ECM connector.
Is there poor contact of ECM
connector?
Repair the poor
contact of ECM
connector.
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary open or
short circuit of har-
ness or temporary
poor contact of
connector may be
the cause.
3 CHECK POWER SUPPLY TO LEAK CHECK
VALVE ASSEMBLY.
Measure the voltage between the leak check
valve assembly connector and engine ground.
Connector & terminal
(R400) No. 5 (+) — Engine ground (–):
Is the voltage 10 V or more? Go to step 4. Repair the power
supply circuit.
4 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM and
the leak check valve assembly.
3) Measure the resistance between leak check
valve assembly and chassis ground.
Connector & terminal
(R400) No. 1 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the short
circuit to ground in
harness between
ECM connector
and leak check
valve assembly
connector.
5 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
Measure the resistance of harness between
ECM connector and the leak check valve
assembly connector.
Connector & terminal
(B135) No. 4 — (R400) No. 1:
Is the resistance less than 1 Ω? Go to step 6. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and the leak check
valve assembly
connector
Poor contact of
coupling connector
15WRX_STI_US_EN.book 402 ージ 20  
EN(STI)(diag)-403
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
6 CHECK LEAK CHECK VALVE ASSEMBLY.
Check the switching valve of the leak check
valve assembly. <Ref. to EC(STI)-45, CHECK
SWITCHING VALVE, INSPECTION, Leak
Check Valve Assembly.>
Is the switching valve of the
leak check valve assembly OK?
Repair the poor
contact in the leak
check valve
assembly connec-
tor.
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
Step Check Yes No
15WRX_STI_US_EN.book 403 ージ 20  
EN(STI)(diag)-404
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FQ:DTC P2420 EVAPORATIVE EMISSION SYSTEM SWITCHING VALVE CON-
TROL CIRCUIT HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-220, DTC P2420 EVAPORATIVE EMISSION SYSTEM
SWITCHING VALVE CONTROL CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
B97
B83
456
123
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
2524
30
987
17 18 19 20
28
21 22 23
29 3231
1234
56
2726
33 34 35
B136C:
B135B:
B136C:
B137D:
EN-10868
20
15
16
18
R1B97
19
17
*
*
B83
J/C
*
3
4
R400
1234
5678
R400
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B550
216
10
B220
11
D27
5
1
6
7
8
B30
B4
B22
C21
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
ECM
SBF-7
VACUUM PUMP
MAIN RELAY
BATTERY
FUSE HOLDER
LEAK CHECK VALVE ASSY
SWITCHING VALVE
PRESSURE SENSOR
: TERMINAL No. OPTIONAL ARRANGEMENT
15WRX_STI_US_EN.book 404 ージ 20  
EN(STI)(diag)-405
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK HARNESS BETWEEN ECM AND
LEAK CHECK VALVE ASSEMBLY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the leak
check valve assembly.
3) Turn the ignition switch to ON.
4) Measure the voltage between leak check
valve assembly and chassis ground.
Connector & terminal
(R400) No. 1 (+) — Chassis ground (–):
Is the voltage 10 V or more? Repair the short
circuit to power in
harness between
ECM connector
and leak check
valve assembly
connector.
Go to step 2.
2 CHECK LEAK CHECK VALVE ASSEMBLY.
1) Turn the ignition switch to OFF.
2) Check the switching valve of the leak check
valve assembly. <Ref. to EC(STI)-45, CHECK
SWITCHING VALVE, INSPECTION, Leak
Check Valve Assembly.>
Is the switching valve of the
leak check valve assembly OK?
Repair the poor
contact in the leak
check valve
assembly connec-
tor.
Replace the leak
check valve
assembly. <Ref. to
EC(STI)-30, Leak
Check Valve
Assembly.>
15WRX_STI_US_EN.book 405 ージ 20  
EN(STI)(diag)-406
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FR:DTC P2431 SECONDARY AIR INJECTION SYSTEM AIR FLOW /PRESSURE
SENSOR CIRCUIT RANGE/PERFORMANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-221, DTC P2431 SECONDARY AIR INJECTION SYSTEM
AIR FLOW /PRESSURE SENSOR CIRCUIT RANGE/PERFORMANCE, Diagnostic Trouble Code (DTC)
Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check the appro-
priate DTC using
the “List of Diag-
nostic Trouble
Code (DTC)”.
<Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Go to step 2.
2 CHECK CURRENT DATA.
1) Turn the ignition switch to ON (engine OFF).
2) Using the Subaru Select Monitor, read the
values in «Sec. Air Piping Pressure», «Mani.
Absolute Pressure» and «Atmosphere Pres-
sure», and compare them with actual atmo-
spheric pressure.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Does the displayed value differ
from the actual atmospheric
pressure by 200 mmHg (27
kPa, 8 inHg, 3.9 psig) or more?
Replace the sec-
ondary air combi-
nation valve (with
built-in pressure
sensor). <Ref. to
EC(STI)-54, Sec-
ondary Air Combi-
nation Valve.>
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
15WRX_STI_US_EN.book 406 ージ 20  
EN(STI)(diag)-407
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FS:DTC P2432 SECONDARY AIR INJECTION SYSTEM AIR FLOW /PRESSURE
SENSOR CIRCUIT LOW
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-222, DTC P2432 SECONDARY AIR INJECTION SYSTEM
AIR FLOW /PRESSURE SENSOR CIRCUIT LOW, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 407 ージ 20  
EN(STI)(diag)-408
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
A:
M/B
F37
B: B143
E40
B143B:
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
F37A:
1234
56789
10 11 12 13 14 15 16 17 18 19 20
12
F11
5
11
15
1
2
9
10
34 7
12 13
8
6
16
14
F9
12
E41
123
456
E40
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
F9
A13
28
1
6
47
E2
B21
46
B550
216
B220
11
10
1
2
3
6
4
1
2
2
60A
10A
14
12
11
13
15
16
6
5
7
10
8
9
4
1
3
2
B10
B20
A5B2
A17B13
A20
A18B12
B4 A8
A19
D9
A29
B27
B20
B8
B137D:
B135B:
B134A:
A16
B14
1
E41 F11
EN-10867
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SECONDARY
AIR PUMP
SECONDARY
AIR COMBINATION
VALVE RH
SECONDARY
AIR PUMP RELAY
SECONDARY
AIR COMBINATION
VALVE RELAY 2
SECONDARY
AIR COMBINATION
VALVE RELAY 1
MAIN SBF
MAIN RELAY
BATTERY
FUSE HOLDER
RELAY HOLDER
SECONDARY AIR
COMBINATION VALVE LH
(WITH BUILT-IN
PRESSURE SENSOR)
15WRX_STI_US_EN.book 408 ージ 20  
EN(STI)(diag)-409
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Turn the ignition switch to ON.
2) Read the value of «Sec. Air Piping Pres-
sure» using Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Sec. Air Piping
Pressure» less than 53.3 kPa
(400 mmHg, 15.8 inHg)?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK POWER SUPPLY OF SECONDARY
AIR COMBINATION VALVE.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the second-
ary air combination valve LH.
3) Turn the ignition switch to ON.
4) Measure the voltage between the second-
ary air combination valve LH connector and
chassis ground.
Connector & terminal
(E40) No. 1 (+) — Chassis ground (–):
Is the voltage 4.5 V or more? Go to step 3. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and secondary air
combination valve
LH connector
Poor contact of
ECM connector
Poor contact of
coupling connector
3 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from ECM.
3) Measure the resistance of harness between
ECM connector and secondary air combination
valve LH connector.
Connector & terminal
(B137) No. 9 — (E40) No. 2:
Is the resistance less than 1 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and secondary air
combination valve
LH connector
Poor contact of
coupling connector
4 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
CONNECTOR.
Measure the resistance between ECM connec-
tor and chassis ground.
Connector & terminal
(B137) No. 9 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 5. Repair the ground
short circuit in har-
ness between
ECM connector
and secondary air
combination valve
LH connector.
5 CHECK FOR POOR CONTACT.
Check for poor contact of the ECM and second-
ary air combination valve LH connector.
Is there poor contact of the
ECM or secondary air combi-
nation valve LH connector?
Repair the poor
contact of the ECM
or secondary air
combination valve
LH connector.
Replace the sec-
ondary air combi-
nation valve LH.
<Ref. to EC(STI)-
54, Secondary Air
Combination
Valve.>
15WRX_STI_US_EN.book 409 ージ 20  
EN(STI)(diag)-410
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FT:DTC P2433 SECONDARY AIR INJECTION SYSTEM AIR FLOW /PRESSURE
SENSOR CIRCUIT HIGH
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-223, DTC P2433 SECONDARY AIR INJECTION SYSTEM
AIR FLOW /PRESSURE SENSOR CIRCUIT HIGH, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 410 ージ 20  
EN(STI)(diag)-411
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
A:
M/B
F37
B: B143
E40
B143B:
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
F37A:
1234
56789
10 11 12 13 14 15 16 17 18 19 20
12
F11
5
11
15
1
2
9
10
34 7
12 13
8
6
16
14
F9
12
E41
123
456
E40
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
F9
A13
28
1
6
47
E2
B21
46
B550
216
B220
11
10
1
2
3
6
4
1
2
2
60A
10A
14
12
11
13
15
16
6
5
7
10
8
9
4
1
3
2
B10
B20
A5B2
A17B13
A20
A18B12
B4 A8
A19
D9
A29
B27
B20
B8
B137D:
B135B:
B134A:
A16
B14
1
E41 F11
EN-10867
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SECONDARY
AIR PUMP
SECONDARY
AIR COMBINATION
VALVE RH
SECONDARY
AIR PUMP RELAY
SECONDARY
AIR COMBINATION
VALVE RELAY 2
SECONDARY
AIR COMBINATION
VALVE RELAY 1
MAIN SBF
MAIN RELAY
BATTERY
FUSE HOLDER
RELAY HOLDER
SECONDARY AIR
COMBINATION VALVE LH
(WITH BUILT-IN
PRESSURE SENSOR)
15WRX_STI_US_EN.book 411 ージ 20  
EN(STI)(diag)-412
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK CURRENT DATA.
1) Turn the ignition switch to ON.
2) Read the value of «Sec. Air Piping Pres-
sure» using Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Sec. Air Piping
Pressure» 133.3 kPa (1,000
mmHg, 39.4 inHg) or more?
Go to step 2. Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
2 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the connector from the second-
ary air combination valve LH.
3) Turn the ignition switch to ON.
4) Read the value of «Sec. Air Piping Pres-
sure» using Subaru Select Monitor.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the value of «Sec. Air Piping
Pressure» 133.3 kPa (1,000
mmHg, 39.4 inHg) or more?
Repair the short
circuit to power in
harness between
ECM connector
and secondary air
combination valve
LH connector.
Go to step 3.
3 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
CONNECTOR.
1) Turn the ignition switch to OFF.
2) Measure the resistance of the harness
between the secondary air combination valve
LH connector and engine ground.
Connector & terminal
(E40) No. 3 — Engine ground:
Is the resistance less than 5 Ω? Go to step 4. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and secondary air
combination valve
LH connector
Poor contact of
ECM connector
Poor contact of
coupling connector
4 CHECK FOR POOR CONTACT.
Check for poor contact of the secondary air
combination valve LH connector.
Is there poor contact of the sec-
ondary air combination valve
LH connector?
Repair the poor
contact of the sec-
ondary air combi-
nation valve LH
connector.
Replace the sec-
ondary air combi-
nation valve LH.
<Ref. to EC(STI)-
54, Secondary Air
Combination
Valve.>
15WRX_STI_US_EN.book 412 ージ 20  
EN(STI)(diag)-413
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FU:DTC P2440 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE
STUCK OPEN (BANK1)
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-224, DTC P2440 SECONDARY AIR INJECTION SYSTEM
SWITCHING VALVE STUCK OPEN (BANK1), Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 413 ージ 20  
EN(STI)(diag)-414
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
A:
M/B
F37
B: B143
E40
B143B:
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
F37A:
1234
56789
10 11 12 13 14 15 16 17 18 19 20
12
F11
5
11
15
1
2
9
10
34 7
12 13
8
6
16
14
F9
12
E41
123
456
E40
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
F9
A13
28
1
6
47
E2
B21
46
B550
216
B220
11
10
1
2
3
6
4
1
2
2
60A
10A
14
12
11
13
15
16
6
5
7
10
8
9
4
1
3
2
B10
B20
A5B2
A17B13
A20
A18B12
B4 A8
A19
D9
A29
B27
B20
B8
B137D:
B135B:
B134A:
A16
B14
1
E41 F11
EN-10867
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SECONDARY
AIR PUMP
SECONDARY
AIR COMBINATION
VALVE RH
SECONDARY
AIR PUMP RELAY
SECONDARY
AIR COMBINATION
VALVE RELAY 2
SECONDARY
AIR COMBINATION
VALVE RELAY 1
MAIN SBF
MAIN RELAY
BATTERY
FUSE HOLDER
RELAY HOLDER
SECONDARY AIR
COMBINATION VALVE LH
(WITH BUILT-IN
PRESSURE SENSOR)
15WRX_STI_US_EN.book 414 ージ 20  
EN(STI)(diag)-415
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK SECONDARY AIR COMBINATION
VALVE FUSE.
Check if the secondary air combination valve
fuse (10 A) is blown out.
Is the fuse blown out? Go to step 2. Go to step 3.
2 CHECK HARNESS BETWEEN FUSE BOX
AND SECONDARY AIR COMBINATION
VALVE RH CONNECTOR.
1) Remove the secondary air combination
valve fuse (10 A) from the fuse box.
2) Disconnect the connectors from the sec-
ondary air combination valve RH and the sec-
ondary air combination valve LH.
3) Measure the resistance between the sec-
ondary air combination valve fuse, secondary
air combination valve RH connector, secondary
air combination valve LH connector and the
chassis ground.
Connector & terminal
(F9) No. 5 — Chassis ground:
(E41) No. 2 — Chassis ground:
(E40) No. 6 — Chassis ground:
Is the resistance 1 MΩ or
more?
Replace the fuse
with a new part,
and connect the
secondary air com-
bination valve RH
connector and the
secondary air com-
bination valve LH
connector.
Go to step 3.
Repair the short
circuit to ground in
harness between
the fuse box and
the secondary air
combination valve
RH connector and
the secondary air
combination valve
LH connector.
3 CHECK SECONDARY AIR COMBINATION
VALVE RH OPERATION.
1) Install the delivery mode fuse.
2) Turn the ignition switch to ON.
3) Perform operation check for the secondary
air combination valve RH using the Subaru
Select Monitor.
NOTE:
For detailed procedures, refer to “System Oper-
ation Check Mode”. <Ref. to EN(STI)(diag)-60,
System Operation Check Mode.>
Does the secondary air combi-
nation valve RH repeatedly
switch to ON and OFF?
Go to step 4. Go to step 6.
4 CHECK DUCT BETWEEN SECONDARY AIR
PUMP AND SECONDARY AIR COMBINA-
TION VALVE RH.
Check the duct between the secondary air
pump and secondary air combination valve RH.
Is there damage, clog or dis-
connection of the duct?
Replace, clean or
connect the duct.
Go to step 5.
5 CHECK PIPE BETWEEN SECONDARY AIR
COMBINATION VALVE RH AND CYLINDER
HEAD.
Check the pipe between the secondary air com-
bination valve RH and cylinder head.
Is there damage, clog or dis-
connection of the pipe?
Replace, clean or
connect the pipe.
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
15WRX_STI_US_EN.book 415 ージ 20  
EN(STI)(diag)-416
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
6 CHECK POWER SUPPLY TO SECONDARY
AIR COMBINATION VALVE RH.
1) Disconnect the connector from the second-
ary air combination valve RH.
2) In the condition of step 3, measure the volt-
age between secondary air combination valve
RH connector and chassis ground.
Connector & terminal
(E41) No. 2 (+) — Chassis ground (–):
Does the voltage repeatedly
change between 10 V and 0 V?
Replace the sec-
ondary air combi-
nation valve RH.
<Ref. to EC(STI)-
54, Secondary Air
Combination
Valve.>
Go to step 7.
7 CHECK HARNESS BETWEEN SECONDARY
AIR COMBINATION VALVE RH AND CHAS-
SIS GROUND.
Measure the resistance between the secondary
air combination valve RH connector and chas-
sis ground.
Connector & terminal
(E41) No. 1 — Chassis ground:
Is the resistance less than 5 Ω? Go to step 8. Repair the open
circuit in harness
between second-
ary air combination
valve RH connec-
tor and chassis
ground.
8 CHECK HARNESS BETWEEN SECONDARY
AIR COMBINATION VALVE RELAY 2 AND
SECONDARY AIR COMBINATION VALVE
RH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the secondary air combination
valve relay 2 from the relay box.
3) Measure the resistance of the harness
between secondary air combination valve relay
2 connector and secondary air combination
valve RH connector.
Connector & terminal
(F9) No. 8 — (E41) No. 2:
Is the resistance less than 1 Ω? Go to step 9. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
secondary air com-
bination valve re-
lay 2 connector
and secondary air
combination valve
RH connector
Poor contact of
coupling connector
9 CHECK SECONDARY AIR COMBINATION
VALVE RELAY 2.
1) Connect the battery to terminals No. 9 and
No. 10 of the secondary air combination valve
relay 2.
2) Measure the resistance between the sec-
ondary air combination valve relay 2 terminals.
Terminals
No. 7 — No. 8:
Is the resistance less than 1 Ω? Go to step 10. Replace the sec-
ondary air combi-
nation valve relay
2. <Ref. to
EN(STI)(diag)-8,
Electrical Compo-
nent Location.>
10 CHECK SECONDARY AIR COMBINATION
VALVE RELAY 2.
Measure the resistance between the secondary
air combination valve relay 2 terminals with the
battery disconnected.
Terminals
No. 7 — No. 8:
Is the resistance 1 MΩ or
more?
Go to step 11. Replace the sec-
ondary air combi-
nation valve relay
2. <Ref. to
EN(STI)(diag)-8,
Electrical Compo-
nent Location.>
11 CHECK SECONDARY AIR COMBINATION
VALVE RELAY 2 POWER SUPPLY.
1) Turn the ignition switch to ON.
2) Measure the voltage between the second-
ary air combination valve relay 2 connector and
chassis ground.
Connector & terminal
(F9) No. 7 (+) — Chassis ground (–):
(F9) No. 10 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 12. Repair the open or
ground short circuit
of power supply
circuit.
Step Check Yes No
15WRX_STI_US_EN.book 416 ージ 20  
EN(STI)(diag)-417
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
12 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 2 CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the ECM connector.
3) Measure the resistance of harness between
ECM connector and secondary air combination
valve relay 2 connector.
Connector & terminal
(B135) No. 20 — (F9) No. 9:
Is the resistance less than 1 Ω? Go to step 13. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and secondary air
combination valve
relay 2 connector
Poor contact of
coupling connector
13 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 2 CONNECTOR.
Measure the resistance between the secondary
air combination valve relay 2 connector and
chassis ground.
Connector & terminal
(F9) No. 9 — Chassis ground:
Is the resistance 1 MΩ or
more?
Go to step 14. Repair the short
circuit to ground in
harness between
ECM connector
and secondary air
combination valve
relay 2 connector.
14 CHECK SECONDARY AIR COMBINATION
VALVE LH OPERATION.
1) Install the delivery mode fuse.
2) Turn the ignition switch to ON.
3) Perform operation check for the secondary
air combination valve LH using the Subaru
Select Monitor.
NOTE:
For detailed procedures, refer to “System Oper-
ation Check Mode”. <Ref. to EN(STI)(diag)-60,
System Operation Check Mode.>
Does the secondary air combi-
nation valve LH repeatedly
switch to ON and OFF?
Go to step 15. Go to step 17.
15 CHECK DUCT BETWEEN SECONDARY AIR
PUMP AND SECONDARY AIR COMBINA-
TION VALVE LH.
Check the duct between the secondary air
pump and secondary air combination valve LH.
Is there damage, clog or dis-
connection of the duct?
Replace, clean or
connect the duct.
Go to step 16.
16 CHECK PIPE BETWEEN SECONDARY AIR
COMBINATION VALVE LH AND CYLINDER
HEAD.
Check the pipe between the secondary air com-
bination valve LH and cylinder head.
Is there damage, clog or dis-
connection of the pipe?
Replace, clean or
connect the pipe.
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, tem-
porary poor con-
tact of connector,
temporary open or
short circuit of har-
ness may be the
cause.
Step Check Yes No
15WRX_STI_US_EN.book 417 ージ 20  
EN(STI)(diag)-418
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
17 CHECK POWER SUPPLY TO SECONDARY
AIR COMBINATION VALVE LH.
1) Disconnect the connector from the second-
ary air combination valve LH.
2) In the condition of step 14, measure the volt-
age between secondary air combination valve
LH connector and chassis ground.
Connector & terminal
(E40) No. 6 (+) — Chassis ground (–):
Does the voltage repeatedly
change between 10 V and 0 V?
Replace the sec-
ondary air combi-
nation valve LH.
<Ref. to EC(STI)-
54, Secondary Air
Combination
Valve.>
Go to step 18.
18 CHECK HARNESS BETWEEN SECONDARY
AIR COMBINATION VALVE LH AND CHAS-
SIS GROUND.
Measure the resistance between the secondary
air combination valve LH connector and chassis
ground.
Connector & terminal
(E40) No. 4 — Chassis ground:
Is the resistance less than 5 Ω? Go to step 19. Repair the open
circuit in harness
between second-
ary air combination
valve LH connector
and chassis
ground.
19 CHECK HARNESS BETWEEN SECONDARY
AIR COMBINATION VALVE RELAY 1 AND
SECONDARY AIR COMBINATION VALVE
LH CONNECTOR.
1) Turn the ignition switch to OFF.
2) Remove the secondary air combination
valve relay 1 from the relay box.
3) Measure the resistance of the harness
between the secondary air combination valve
relay 1 and secondary air combination valve LH
connector.
Connector & terminal
(F9) No. 3 — (E40) No. 6:
Is the resistance less than 1 Ω? Go to step 20. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
secondary air com-
bination valve re-
lay 1 connector
and secondary air
combination valve
LH connector
Poor contact of
coupling connector
20 CHECK SECONDARY AIR COMBINATION
VALVE RELAY 1.
1) Connect the battery to terminals No. 1 and
No. 2 of the secondary air combination valve
relay 1.
2) Measure the resistance between the sec-
ondary air combination valve relay 1 terminals.
Terminals
No. 3 — No. 4:
Is the resistance less than 1 Ω? Go to step 21. Replace the sec-
ondary air combi-
nation valve relay
1. <Ref. to
EN(STI)(diag)-8,
Electrical Compo-
nent Location.>
21 CHECK SECONDARY AIR COMBINATION
VALVE RELAY 1.
Measure the resistance between the secondary
air combination valve relay 1 terminals with the
battery disconnected.
Terminals
No. 3 — No. 4:
Is the resistance 1 MΩ or
more?
Go to step 22. Replace the sec-
ondary air combi-
nation valve relay
1. <Ref. to
EN(STI)(diag)-8,
Electrical Compo-
nent Location.>
22 CHECK SECONDARY AIR COMBINATION
VALVE RELAY 1 POWER SUPPLY.
1) Turn the ignition switch to ON.
2) Measure the voltage between the second-
ary air combination valve relay 1 connector and
chassis ground.
Connector & terminal
(F9) No. 4 (+) — Chassis ground (–):
(F9) No. 1 (+) — Chassis ground (–):
Is the voltage 10 V or more? Go to step 23. Repair the open or
ground short circuit
of power supply
circuit.
Step Check Yes No
15WRX_STI_US_EN.book 418 ージ 20  
EN(STI)(diag)-419
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FV:DTC P2441 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE
STUCK CLOSED (BANK1)
NOTE:
For the diagnostic procedure, refer to DTC P2440. <Ref. to EN(STI)(diag)-413, DTC P2440 SECONDARY
AIR INJECTION SYSTEM SWITCHING VALVE STUCK OPEN (BANK1), Diagnostic Procedure with Diag-
nostic Trouble Code (DTC).>
FW:DTC P2442 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE
STUCK OPEN (BANK2)
NOTE:
For the diagnostic procedure, refer to DTC P2440. <Ref. to EN(STI)(diag)-413, DTC P2440 SECONDARY
AIR INJECTION SYSTEM SWITCHING VALVE STUCK OPEN (BANK1), Diagnostic Procedure with Diag-
nostic Trouble Code (DTC).>
FX:DTC P2443 SECONDARY AIR INJECTION SYSTEM SWITCHING VALVE
STUCK CLOSED (BANK2)
NOTE:
For the diagnostic procedure, refer to DTC P2440. <Ref. to EN(STI)(diag)-413, DTC P2440 SECONDARY
AIR INJECTION SYSTEM SWITCHING VALVE STUCK OPEN (BANK1), Diagnostic Procedure with Diag-
nostic Trouble Code (DTC).>
23 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 1 CONNECTOR.
1) Turn the ignition switch to OFF.
2) Disconnect the ECM connector.
3) Measure the resistance of harness between
ECM connector and secondary air combination
valve relay 1 connector.
Connector & terminal
(B135) No. 8 — (F9) No. 2:
Is the resistance less than 1 Ω? Go to step 24. Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Open circuit in
harness between
ECM connector
and secondary air
combination valve
relay 1 connector
Poor contact of
coupling connector
24 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR COMBINATION VALVE
RELAY 1 CONNECTOR.
Measure the resistance between the secondary
air combination valve relay 1 connector and
chassis ground.
Connector & terminal
(F9) No. 2 — Chassis ground:
Is the resistance 1 MΩ or
more?
Repair the poor
contact of ECM
connector.
Repair the short
circuit to ground in
harness between
ECM connector
and secondary air
combination valve
relay 1 connector.
Step Check Yes No
15WRX_STI_US_EN.book 419 ージ 20  
EN(STI)(diag)-420
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FY:DTC P2444 SECONDARY AIR INJECTION SYSTEM PUMP STUCK ON
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-225, DTC P2444 SECONDARY AIR INJECTION SYSTEM
PUMP STUCK ON, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
15WRX_STI_US_EN.book 420 ージ 20  
EN(STI)(diag)-421
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
ECM
A:
M/B
F37
B: B143
E40
B143B:
89
19 20
1234 567
10 11 12 13 14 15 16 17 18
F37A:
1234
56789
10 11 12 13 14 15 16 17 18 19 20
12
F11
5
11
15
1
2
9
10
34 7
12 13
8
6
16
14
F9
12
E41
123
456
E40
B220
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
F9
A13
28
1
6
47
E2
B21
46
B550
216
B220
11
10
1
2
3
6
4
1
2
2
60A
10A
14
12
11
13
15
16
6
5
7
10
8
9
4
1
3
2
B10
B20
A5B2
A17B13
A20
A18B12
B4 A8
A19
D9
A29
B27
B20
B8
B137D:
B135B:
B134A:
A16
B14
1
E41 F11
EN-10867
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SECONDARY
AIR PUMP
SECONDARY
AIR COMBINATION
VALVE RH
SECONDARY
AIR PUMP RELAY
SECONDARY
AIR COMBINATION
VALVE RELAY 2
SECONDARY
AIR COMBINATION
VALVE RELAY 1
MAIN SBF
MAIN RELAY
BATTERY
FUSE HOLDER
RELAY HOLDER
SECONDARY AIR
COMBINATION VALVE LH
(WITH BUILT-IN
PRESSURE SENSOR)
15WRX_STI_US_EN.book 421 ージ 20  
EN(STI)(diag)-422
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK SECONDARY AIR PIPING PRES-
SURE.
1) Turn the ignition switch to ON.
2) Using the Subaru Select Monitor, read the
value of «Sec. Air Piping Pressure», and com-
pare with the actual atmospheric pressure.
NOTE:
For detailed operation procedures, refer to
“READ CURRENT DATA FOR ENGINE”. <Ref.
to EN(STI)(diag)-36, Subaru Select Monitor.>
Is the difference between «Sec.
Air Piping Pressure» and atmo-
spheric pressure 50 mmHg (6.7
kPa, 2.0 inHg, 0.97 psig) or
less?
Go to step 2. Replace the sec-
ondary air combi-
nation valve LH.
<Ref. to EC(STI)-
54, Secondary Air
Combination
Valve.>
2 CHECK HARNESS BETWEEN ECM AND
SECONDARY AIR PUMP RELAY CONNEC-
TOR.
1) Turn the ignition switch to OFF.
2) Remove the secondary air pump relay from
the relay holder.
3) Measure the resistance between the sec-
ondary air pump relay connector and engine
ground terminals.
Connector & terminal
(F9) No. 13 — Engine ground:
Is the resistance 1 MΩ or
more?
Go to step 3. Repair the short
circuit to ground in
harness between
ECM connector
and secondary air
pump relay con-
nector, and go to
the next step. Go to
step 3.
3 CHECK SECONDARY AIR PUMP FUSE.
1) Disconnect the secondary air pump con-
nector.
2) Install the secondary air pump relay to the
relay holder.
3) Check the MAIN SBF and the secondary air
pump fuse (60 A) for blown out.
Is the fuse blown out? Replace the fuse
with a new part,
and go to the next
step. Go to step 4.
Go to step 4.
4 CHECK SECONDARY AIR PUMP POWER
SUPPLY.
1) Disconnect the positive (+) terminal after
disconnecting the negative (–) terminal of bat-
tery.
2) Measure the resistance between secondary
air pump connector and battery cable positive
terminal.
Connector & terminal
(F11) No. 2 — battery cable positive ter-
minal:
Is the resistance 1 MΩ or
more?
Go to step 6. Go to step 5.
5 CHECK SECONDARY AIR PUMP RELAY.
1) Remove the secondary air pump relay from
the relay holder.
2) Measure the resistance between the sec-
ondary air pump relay terminals.
Terminals
No. 11 — No. 14:
Is the resistance 1 MΩ or
more?
Repair the short
circuit to power of
the secondary air
pump, and go to
the next step. Go to
step 6.
Replace the sec-
ondary air pump
relay. <Ref. to
EN(STI)(diag)-8,
LOCATION, Elec-
trical Component
Location.> After
replacement, go to
the next step. Go to
step 6.
6 CHECK SECONDARY AIR PUMP.
Check the appearance of secondary air pump
and the condition of impeller.
Is the secondary air pump free
from deformation, cracks and
other damages? And does the
impeller rotate smoothly?
End. Replace the sec-
ondary air pump.
<Ref. to EC(STI)-
53, Secondary Air
Pump.>
15WRX_STI_US_EN.book 422 ージ 20  
EN(STI)(diag)-423
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
FZ:DTC P2530 IGNITION SWITCH RUN POSITION CIRCUIT
DTC DETECTING CONDITION:
Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to GD(STI)-226, DTC P2530 IGNITION SWITCH RUN POSITION CIR-
CUIT, Diagnostic Trouble Code (DTC) Detecting Criteria.>
TROUBLE SYMPTOM:
Improper idling
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
WIRING DIAGRAM:
Engine Electrical System ENGINE TYPE EJ (WITHOUT PUSH BUTTON START) <Ref. to WI-198, EN-
GINE TYPE EJ (WITHOUT PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
Engine Electrical System ENGINE TYPE EJ (WITH PUSH BUTTON START) <Ref. to WI-218, ENGINE
TYPE EJ (WITH PUSH BUTTON START), WIRING DIAGRAM, Engine Electrical System.>
34
40
WP
OP
WP
OP
B72
B550
216
B550
1024
B220
11
12
10
13
B134A:
B135B:
B136C:
B137D:
A3
A6
D1
D3
A4
36
35
E2
B21
C30
C2
B13
D7
C1
B220 B225
10 11
12
13
14 15
16
18
19 21 22
20
17
24
5
3
17
9
8
6
32 33
34
35
28262423
25
27
29
30
31
36 37
38
40
41 43 44
42
39
567
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17 18 19
20 21
29 30 31 32 33 34 35
B135B:
567
8
21
9
43
10
22 23
11 12 13 14 15
24 25
26
16 17
18 19 20 21
27 28 29 30 31
B137D:
1610 11 12 13 14 15
25
24
30
987
17 18 19 20
28
21 22
23
29 3231
1234
56
2726
33 34 35
B136C:
56 7
8
21
9
43
10
2422 23 25
11 12 13 14 15
26 27
28
16 17
18 19 20 21
33 3429
3230 31
B134A:
B21
123456789
10 11
12 13 14 15 16 17 18 19 20
21 22
23 24 25 26 27 28 29 30 31 32 33
34 35
42 43
36 37 38 39
48 49 50 51 52 53 54
40 41
44 45 46 47
14
B225
36 37
EN-10853
WP
OP
B72
7856
3412
101
242322 272625212019
5
14
13
18
432
17
7
16
698
15
11 12
B550
SBF-7
SBF-6
ECM
: WITHOUT PUSH BUTTON START
: WITH PUSH BUTTON START
IG RELAY 1
(PUSH BUTTON
START)
BATTERY
MAIN
RELAY
FUSE
HOLDER
FUSE
HOLDER
M/B No. 13
F/B No. 12
IGNITION
SWITCH
MAIN SBF
15WRX_STI_US_EN.book 423 ージ 20  
EN(STI)(diag)-424
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
Step Check Yes No
1 CHECK ECM CONNECTOR.
Check the connecting condition of ECM con-
nector.
Is the ECM connector correctly
connected?
Go to step 2. Connect the ECM
connector cor-
rectly.
2 CHECK INPUT VOLTAGE OF ECM.
1) Turn the ignition switch to ON.
2) Measure the voltage between ECM connec-
tor and chassis ground while wiggling the har-
ness between ECM connector and ignition
switch connector (for models without push but-
ton start), or between ECM connector and IG
relay 1 (push button start) connector (for mod-
els with push button start).
Connector & terminal
(B136) No. 30 (+) — Chassis ground (–):
Is the voltage 8 V or more all the
time?
Even if DTC is
detected, the cir-
cuit has returned to
a normal condition
at this time. Repro-
duce the failure,
and then perform
the diagnosis
again.
NOTE:
In this case, the fol-
lowing items may
be the cause of
fault.
Model without
push button start
Open or short
circuit to ground
in harness be-
tween ECM
connector and
ignition switch
connector
Poor contact
of ignition
switch connec-
tor
Poor contact
of ignition
switch
Model with push
button start
Open circuit
or short circuit
to ground in har-
ness between
ECM connector
and IG relay 1
(push button
start) connector
Poor contact
in IG relay 1
(push button
start) connector
Poor contact
in IG relay 1
(push button
start)
Repair the harness
and connector.
NOTE:
In this case, repair
the following item:
Model without
push button start
Open or short
circuit to ground in
harness between
ECM connector
and ignition switch
connector
Poor contact of
ignition switch con-
nector
Poor contact of
ignition switch
Faulty fuse (F/B
No. 12)
Model with push
button start
Open circuit or
short circuit to
ground in harness
between ECM con-
nector and IG relay
1 (push button
start) connector
Poor contact in
IG relay 1 (push
button start) con-
nector
Poor contact in
IG relay 1 (push
button start)
Faulty fuse (F/B
No. 12)
15WRX_STI_US_EN.book 424 ージ 20  
EN(STI)(diag)-425
Diagnostic Procedure with Diagnostic Trouble Code (DTC)
ENGINE (DIAGNOSTICS)
GA:DTC P2610 ECM/PCM INTERNAL ENGINE OFF TIMER PERFORMANCE
DTC DETECTING CONDITION:
Detected when two consecutive driving cycles with fault occur.
GENERAL DESCRIPTION <Ref. to GD(STI)-227, DTC P2610 ECM/PCM INTERNAL ENGINE OFF TIM-
ER PERFORMANCE, Diagnostic Trouble Code (DTC) Detecting Criteria.>
CAUTION:
After servicing or replacing faulty parts, perform Clear Memory Mode <Ref. to EN(STI)(diag)-59, OP-
ERATION, Clear Memory Mode.>, and Inspection Mode <Ref. to EN(STI)(diag)-43, PROCEDURE, In-
spection Mode.>.
GB:DTC U0073 CONTROL MODULE COMMUNICATION BUS OFF
NOTE:
For the diagnostic procedure, refer to LAN section. <Ref. to LAN(diag)-2, Basic Diagnostic Procedure.>
GC:DTC U0122 CAN (VDC) DATA NOT LOADED
NOTE:
For the diagnostic procedure, refer to LAN section. <Ref. to LAN(diag)-2, Basic Diagnostic Procedure.>
GD:DTC U0155 LOST COMMUNICATION WITH INSTRUMENT PANEL CLUSTER
(IPC) CONTROL MODULE
NOTE:
For the diagnostic procedure, refer to LAN section. <Ref. to LAN(diag)-2, Basic Diagnostic Procedure.>
GE:DTC U0416 CAN (VDC) DATA ABNORMAL
NOTE:
For the diagnostic procedure, refer to LAN section. <Ref. to LAN(diag)-2, Basic Diagnostic Procedure.>
GF:DTC U0423 INVALID DATA RECEIVED FROM INSTRUMENT PANEL CLUS-
TER CONTROL MODULE
NOTE:
For the diagnostic procedure, refer to LAN section. <Ref. to LAN(diag)-2, Basic Diagnostic Procedure.>
Step Check Yes No
1 CHECK FOR ANY OTHER DTC ON DISPLAY. Is any other DTC displayed? Check DTC using
“List of Diagnostic
Trouble Code
(DTC)”. <Ref. to
EN(STI)(diag)-86,
List of Diagnostic
Trouble Code
(DTC).>
Replace the ECM.
<Ref. to FU(STI)-
56, Engine Control
Module (ECM).>
NOTE:
The soak timer IC
is built into the
ECM.
15WRX_STI_US_EN.book 425 ージ 20